I like that you can access Apple's Camera from the lock screen. When I use a camera replacement app, ProCamera is the camera app I'm likely to use. It's fast, powerful, and lets me get a lot of shots if I need them. It's got studio and effects modules, but they're out of site until you need them.
For sheer power and versatility in a camera app, you can't beat 645 PRO. It's got about every camera tool you can pack into an iPhone camera replacement app, including separate focus and exposure locks, histogram, and a cool low light mode that can expose an image for up to 1 second. It's not as fast shot-to-shot as ProCamera, which is why I use ProCamera.
Camera+ is the best all-around camera app. Its camera is good and the in-app filters are better than most other commercial apps. There's a reason it's usually the number 1 paid photo app.
=M=