The agony and ecstasy of the modern, high-tech car

He’d bought the car for the 354-horsepower, 5.4-liter V-8 engine. It wasn’t fast by any measure of today, but it was still a visceral kick in the pants. Whenever he floors it, an unholy bellow issues from its guts. "Still, a Kia Optima is far more advanced than this hooptie." (Indeed, the Kia is available with heated rear seats, surround cameras, and a rear trunk that opens when you approach it with the key.)

This is one of the problems with a once-expensive sedan stuffed with once-new tech, as my friend had discovered: the features become liabilities. Much of it is nearly useless when it becomes outdated. And once the car is no longer under warranty, those frivolous tidbits can be very ludicrously expensive to fix or update.

All of this went through my mind as I recently drove a brand new BMW 7 Series from New York to Boston and back. Similar to the Mercedes S-Class, BMW uses its flagship executive sedan to lead the company’s technological charge.

There are more powerful cars in the BMW range, and the hybrid i8 sports coupe is more technologically advanced, at least when it comes to the powertrain. But the 750i xDrive — which is in a luxury sedan space race with the S-Class, Audi’s A8, and the Lexus LS 600h — is still the test bed for nifty features and BMW’s craziest new tech.

We’ve already reviewed the new 7 Series, but a day’s drive is different than living with a car for more than a week and 500-plus miles. During that time, I paid special attention to the tech that I found useful. Some of it will surely pass the test of time. Other bits were frivolous or downright frustrating.

The base price on the car was $97,400, a not insignificant buy-in. Wi-Fi, a heads-up display, a nav system, and wireless charging are all included in that. But there was another $31,000 of options included — yep, more than the entire cost of a well-optioned Kia Optima SX — pushing the sticker to $128,445.

Here’s a rundown of the worthwhile tech I loved, and the stuff that I didn’t. The choices might surprise you.

First, the great: the latest-generation heads-up display. GM was the first company to widely use a projector on the dashboard to beam a translucent image of the speedometer and other info onto the windshield in front of the driver. I first discovered it on a Corvette Z06 more than a decade ago, a car where it was especially useful since you almost always found yourself speeding.

BMW was the first German carmaker to adopt the technology, and it has gotten better and better over the years, adding color and more information, including directions from the nav. The latest system has a projection area that is 75 percent larger than the previous generation, and it is easily the best I’ve ever seen. It is in full color, amazingly sharp, and the map projection changes to show the most relevant information as you near a turn, including a full map overlay. It allows you to negotiate even the most complex turns and routes off freeways. It even made the warren of streets that is downtown Boston simple to navigate.

BMW’s iDrive 5.0 is pretty much flawless, and the voice control actually works when inputting addresses. By contrast, I’ve had zero luck with Audi’s voice input on its brand new cars. On a recent trip in LA, I resorted to just using my iPhone to navigate. Audi’s latest offerings have a new interior which it calls a "virtual cockpit" which includes full-color Google Earth maps on the instrument cluster. As a concept it is quite cool, but in reality you have to look down to orient yourself, taking your eyes off the road. BMW’s choice to continue refining the heads-up display is the right call. Also, the nav system works with a forward-facing camera that recognizes speed limit signs. It posts the speed limit in the display, and often captures the sneaky changes through small towns that local authorities love to exploit.

Next, the good: traffic jam assistant. Slow traffic is the worst. But I’m a Type A and have a very hard time letting a car "drive" itself, and that usually includes using active cruise control. Tesla is pushing hard into the autonomous arena, as are Mercedes and Audi. The latest S-Class’ semi-autonomous systems work well, but I find the stalk-operated controls maddening. The BMW’s system, alternatively, is operated via buttons on the steering wheel that you can actually see.

I got stuck in clogged traffic on my way back into Manhattan, and the active cruise control gets the car moving again even when you’ve been stopped for up to 30 seconds. With the traffic jam assistant also activated, you can keep a lazy hand on the wheel and it generally stays within the lanes. I still don’t have 100 percent confidence, as poor lane markings can confuse any current system. (Tesla’s Elon Musk has noted that this is a challenge for his Autosteer system as well.) The takeaway, though, is that it’s easy enough for your parents to figure out — and it actually works, making bad traffic more tolerable.

The interesting: BMW Display Key. A fob is the one piece of your car you haul around with you, so why not make it cool? This one has a small color touchscreen that performs very basic functions if you are within range (a very important point). You can see the range and verify that it is locked. You can also set a timer to warm up or cool the vehicle. Again, it works and is easy to program. It is oversized, though, and will fight for pocket space in your jeans, so be warned unless you’re partial to carrying around a bag of some sort. Also, you’ll soon be doing all of this stuff and more on your cell phone for most any new car these days.

The silly: the $350 ambient air package, which perfumes the air with your choice of several scents. This is the new-age version of a mirror-hanging pine tree. Mercedes also did it first and with zanier scents like "Nightlife Mood." (You can’t make this stuff up.)

The abject failure: the gesture control system. I get the allure of controlling stuff via gestures, a la Minority Report. This is BMW’s first stab at that. And it would seem to be a relatively benign attempt, since nothing vitally important is controlled: just the stereo volume and the acceptance of an incoming call. A sensor in the roof is supposed to recognize specific gestures, like a finger twiddling motion to turn the volume up or down. Since you can easily control volume on the steering wheel, or a knob in the center console, it’s mostly a party trick to impress passengers anyhow.

It only occasionally worked though, often leaving me to idiotically circle my finger while pointing at the nav screen. When it did operate, it usually lowered or increased the volume more than I wanted.

The real problem were motions interpreted as a gesture. Reaching toward the forward cup holders to retrieve my coffee mug repeatedly muted the stereo completely. It began as an annoyance, but by the week’s end (and my general coffee intake), my passenger pronounced, "This car sucks."

Which makes up my final additional note: it’s the frivolous and seemingly unimportant tech that is most likely to annoy you day in and day out. Something as slight as an irritating gesture control can potentially turn someone off an entire car.

The good news is that when someone buys the 2016 750i in 15 years, the gesture-motion sensors probably will have stopped working anyhow.