TwitPic has long been one of Twitter's key services, providing image hosting for tweets since 2008 — now, there's finally a dedicated TwitPic iPhone app (with an Android app promised to come later this month), though it's hard to say if it'll find an audience amongst the many other photo-sharing apps available. The app itself couldn't be more simple in usage and design. Upon launching and logging in with your Twitter credentials, users are presented with a stream of images that the people they follow have posted to TwitPic; you can easily switch over to view "popular" trending images as well. Unfortunately, nothing posted to other image services (like Instagram or Twitter's default image host) are shown, so your milage will vary in terms of how engaging or useful this stream is.
The main attraction is the giant camera button
The main attraction is the giant camera button though — from there, you can upload an image from your photo library (including your Photo Stream, if you use it) or take a new one. The built-in camera supports photos, video, both the front and back shooters, and the flash... but there's no option for HDR images like in the native iOS camera app. Once you've shot or selected your image, TwitPic provides users with the now-standard editing options — there's a variety of Instagram-ish filters, some generic "enhance" effects, as well as cropping, orientation, and brightness controls. Overall, it's nice to see some options to tweak and improve your pictures, but with Instagram and a number of other high-quality camera apps available, these features are essentially table stakes if you're launching an image-focused app.
After doing your editing, you can add a tweet-caption and post the photo in your Twitter stream as well on Twitpic's site. Overall, the app works exactly like you'd expect, but Instagram's dominance has rendered an app like this somewhat moot. Since the iPhone's Twitter client defaults to Twitter's own image hosting rather than TwitPic, your stream of photos from users you follow might be quite bare — our iPhone only showed us a single lonely image that was recently posted by our followers. With the combined dominance of Instagram and Twitter's native solution (not to mention the direct photo uploading integrated into iOS 5), there might not be much room for TwitPic, well-designed though it may be.