Mmm.. so Android veterans..
What categories of apps am I missing out on through ignorance right now?

EDIT:
Also, I'm looking for a Calendar front-end which is easy to see and interact with on a 4" screen. The built-in Google app sucks -- fonts too small and it's just dumb in many other ways.

I want something like the PalmOS calendar I've been using for years here. Readable, and thought-out.