1) Critting is harder work than it looks. It is always tricky to tell someone that something is wrong. Particularly if it is done using Track Errors and comments. The secret is in the wording.
2) Critting is good for writers in that they learn from other people's mistakes. Nothing like writing that someone should avoid a certain mistake only to realize that you're doing exactly the same.
3) Getting Critted is good in that it highlights my most atrocious writing habits. No one is immune to this one, but these are some of the ones that get picked out most often...
- Characters appearing with zero introduction. I have this way of assuming that people already know who is who. I got one crit partner lost completely because of this and my next habit.
- Too few (believe it or not) tags. Attributing the actions of one party while the other was the one who was speaking... Yeah... Lots of work in dialogue here...
- Word and phrase repetitions. While I have no love for one particular word or phrase, some of them pop up in the same paragraph or close enough to each other that the reader is annoyed.
So... what nasty habits have you picked up in your writing?