I had an unfunded ToS account for 5 months before funding it. I used it to do paper trading. I can't speak to access to such features as ThinkBack which gives you access to historical data.
Customer service is still excellent. However, requests for things that would be approved without much fuss are now on hold pending decisions by their new owner, TD Ameritrade. And initiatives like their iPAD application seem to be on indefinite hold. I fear this merger will take away from ToS what made it so attractive to many of us, i.e. their dynamism and willingness to me a maverick.
Meanwhile, I am still with them. Other than granting access to things I "want" rather than "need," I'm pretty happy.
I can't give you any information relative to other choices because I am not very familiar. The only additional data point is that my son had a substantial account with Zecco and moved it to ToS after he saw what I could do.
Also, they have an options metric called "Probability of Touching." They are the only one I know of who has it and it is critical to my strategy.