I often play 2 round table at once. But I have found that I can't play 2 tables if they are different.

If I play 1 limit table and 1 no-limit table, I get screwed up. If I play 1 $10 NL table and 1 $25 NL table I get screwed up. I tend to confuse the betting styles on the tables. (bet too much on the smaller limit, too little on the bigger limit) I have never tried 2 tournaments at once, but I would imagine this would be similar if the blinds were at different levels.

Also, I wouldn't recomend playing 2 tables if one of them is small. If there are only 2-3 people at a table, the action is just too quick to manage a second table.

But if I get into a big table, I almost always look for a second table.

As far as the betting styles, you can always play catch up. When the bet comes around to you, look who has done what. All the information is sitting on the table for you.