Users don't distinguish between poor UI performance and"code stutters". The "negligble" sub-1ms stutters are a real problem in practice. and it's not just limited to poor code. Sometimes, no matter what you'll see GC being called, there's no way around it. There are background threads that are doing all sorts of things, which very well might be getting GC'd. Theres also a lot of things you can't reasonably avoid, like allocations from Iterators, etc. There are literally thousands of forum and blog posts discussing this online.

Garbage Collection very slow on Android with latest stable line http://groups.google.com/group/v8-users/browse_thread/thread...

How can I avoid garbage collection delays in Java games http://stackoverflow.com/questions/2484079/how-can-i-avoid-g...

Avoiding garbage collection for smooth 2d animations Options

http://groups.google.com/group/android-developers/browse_thr...

Image tiling on Android, garbage collector slows down http://stackoverflow.com/questions/7916021/image-tiling-on-a...