Honestly, you guys are shooting yourselves in the foot by not offering a true free trial. Limiting people to these specific weekends won't give you as much growth as you want. What about people who are otherwise interested, but work weekends?
You might want to take a lesson from Rift. Before launch they gave out beta keys like popcorn. Pretty much anyone who wanted to try the game could and got to play as much as they wanted in the weeks leading up to release. THAT is how you market an untried game. The people that like it will stay, the ones who don't won't.
I wasn't about to shell out $60 for a game that I had no idea if I would enjoy and couldn't resell if I hated. After playing this first trial weekend, I did purchase my retail copy. Give people the freedom to try it on their own terms and you might start to see the growth you want.
Edit: The free trial did not force us to pay upon reaching level 10. The limitations they gave are here: http://www.swtor.com/info/faq/game#q400211