Things I really expected google to address at I/O.
Google clearly tried to proof that they can update core android things without users having to wait for month or years for an update. But what I'm really missing is an update of the youtube app. It's in my opinion one of the ugliest google apps out there and clearly needs an update to better fit in with new apps like the new maps, keep and the new play store. The same can be said about gmail - also not really pretty.
Things that are google/nexus specific is that the dialer/phone app could also use an update - it's really really ugly and the strict distinction between all of your contacts and the dialer is also not good. Also I would like to see the option to add imap accounts to the gmail app - or improve the default mail app. Not every company uses gmail. The same can be said for the stock gallery app - not really an eye catcher.
I think those are reasonable requests and I really hope google will address them soon.