Playing Multiple Tables

[Damn_Squirrels]

I've 'only' played a few thousand hands online, but am wondering about multiple tables. I'm sure I can eek out slightly more if I concentrate on one table (getting a feel for other players, etc.), but easily get bored and can start to loosen up after a while. So I'm wondering about your opinion(s) on how much one's winning percentage suffers by playing multiple tables vs. focusing on one. I've started to track my game logs, but don't have enough data to determine anything with certainty. What has been your experience with win rates on multiple tables, and when/how did you determine it was profitable?

Help?

PS-I did a search on previous threads to try and find something about this topic, but lost patience after 15 minutes of snooping. If this has been covered before and you could point me to it that would be fine as well.