Charlie-
Here are a few comments:
1) Unless you live near a cardroom that offers unique tournaments, I doubt that you have played enough live single table tourneys to compare to your online experience. I've played live in AC and Vegas and have never seen 1 table tourneys offered (other than satellites).
2) You can develop reads on you opponents online as well. Just think about it a bit and read a few of the posts here. Admittedly, it is far easier to pick up a tell in person. Personally, I think tells are pretty overrated in live limit hold em play. I know people look for these things and you can usually tell who is so I often toss in a reverse tell when I play live.
(Unrelated to the reverse tell)...Once I had a tell reader to my left and I raised preflop with AK and he called JT offsuit cold and everyone else folded so it was heads up. He spiked a 10 on the turn and checked the river and shouted "I knew it" when I turned over my unimproved AK. As he was raking the pot, I said, you knew what...that you were an underdog before the flop and after the flop?!?!!? Point is, I didn't bluff, I played it straight and this guy thought he read something. To this day I have no idea what he "knew."
3) Some have said that online players are tougher than live players at the same limit. I'm on the fence here. I do not play enough live limit hold em to make a fair comparison. Online I'm dealt almost 3x the number of hands compared to the same time period live. I'm convinced that while I've only played online a short period of time, I've already played far more online hands than live hands due to the speed of the game.
In my experience, I've played VERY tough 5/10 online and wild and crazy 5/10 in person. I've played crazy 8/16 and 10/20 live and crazier 10/20 online. I've played easy and tough 2/4 and 3/6 online and live. I think it varies.
4) The sturcture of the single table tournaments does not necessarily reward the best play. After the first couple of rounds the blinds are so large that you often have to play hands that you would never play. I've had moderate success at these tournaments but I generally play only when I can't find a ring game to my liking.
If you play online at the larger sites, it is VERY difficult to get to know your opponents since the tables turnover so frequently. MOre importantly, unless you are playing high buy-in single table tournaments at strange hours of the day, the likelihood of you seeing the same players in the tourneys is slim. Because of this, IMHO, it is important to have a SOLID game steeped in fundamentals. I categorize my opponents generally and go from there.
ONE TIP: GET HAND HISTORIES FREQUENTLY. At most limits online the hands will go to a showdown. If there is play that seems strange to you, the winning hand is unexpected, or players with whom you are not familiar order the hand history immediately. It will show you the final hands of everyone who went to showdown. At that point you can make general assumptions about your opponents' play in various situations when they hold certain cards. This is invaluable. I find that it makes it easier for me to know "what" kind of players I'm playing with then I can focus on my game.