I have been using IB for some 10 years, and I think they are very good.
If you only need internet trading, they are fast, cheap and efficient.
Also, they seem one of the safest brokers around. (Check their financials.)
On the negative side, if you want/need to call them and solve some arcane problem, or need to use their customer support, they are average, at best. (I'm happy with them because I almost never have to do that...)