Robfunk-
Here are a few random thoughts from someone who is far from an authority on the topic:
There are people who make a living playing online poker. Your term "good coin" is relative. What you view as "good coin" some may view as pocket change.
I've played online for a while and find that it is one of the greatest movements for all my hobbies. It's something I've always enjoyed doing but couldn't do often given that I live in the live poker wasteland of the NY/NJ area. The once/twice a month game with my friends just doesn't cut it. I stick to the major rooms (or those with which I'm familiar) since they offer everything I need. One could argue that you can find better bonuses or softer games elsewhere but for me I'll only play at Party/Empire, PokerStars, Paradise and maybe Ultimate and WSEX.
What bothers me most about online play is the potential for cheating, slow play, intentional disconnects, and the fact that I don't feel the cards and chips. Cheating does happen but in my experience it happens so infrequently and/or the culprits are so bad at it that the affect on what I need to get out of my experience is minimal. If I made a living at online poker I might feel differently since every dollar counts and losing that $20 big bet to someone who intentionally disconnects means a bit more than it does to me at this point. Cheating/angle shooting has cost me $$ but given what I have taken out of the game and the alternative (NOT PLAYING) it is well worth it.
Regarding games, the best games to learn/play if you are in it for the money are those where the edge for good players is maximized/most beneficial. IMO, if you are a very good player at no-limit, pot-limit, and omaha you can do well since most people don't know those games as well and you can exploit players' weaknesses.
Tips:
recreational: have fun and don't play over your head.
pro: keep meticulous records and be professional (treat it like a job rather than a game).