The thing is, I searched for a long time around the internet, and in terms of reviews you see Jamplay score better than Guitartricks. Tried it out for half a year and wasn't satisfied. There are some cool features like the webcam sessions ( perhaps that will happen in the future with Guitartricks ) but there were loads of needless features, like community thing building. But that shouldn't matter as long as the lessons are great.
I found their lessons very differing in quality. There were some great instructors there but also a lot of instructors who did uuuhm and just talked through there lessons way too slow. Here at Guitartricks the instructors, so far as I discovered, are really able to teach. Also I find the layout of Guitartricks much more appealing.
Just wanted to share my thoughts ;-)
JJ