I have actually taken 3 courses from 3 different companies. Here are my thoughts on each.
Powerscore: Great materials. I took their course about 2 years ago the first time I studied forthe lsat. I was working 60-70 hours a week so many times i would have to miss a session and review at a later date (their website allows you to recall past lectures). Overall the course isn't too bad and their instructors are pretty responsive. That said, the online portion of the course is hard to sit through, especially if you're having to catch up with a session after it was held. Their intentions were decent, but I think that the overall format of the online course leave something to be desired. I was more interested in online lectures and their format is like sitting through a powerpoint slide with someone narrating. Also, there is a lot of stop/start. Their course materials are more than adequate, and with the materials you probably don't need the lectures. However, if that's youre approach just buy all three bibles. The one thing I dislike about them is they classify "inference" (most strongly support questions) as "strengthen" questions.
Fast forward 2 years and I decided to make anothe attempt at the LSAT. (I was working much less this time around)
Testmasters: Their methodology is very good (very similar to powerscore's); however, their online course is not worth the money. For $900+ you get access to course books with no answer keys and online materials that you can't print off and study at a later date. Also, once you finish with particular section you can't return to it later. I also didn't care for the fact that their online text is somewhat fuzy and they don't give you any subject headings or highlight any main ideas. You are essentially paying for a virtual textbook that doesn't really go out of it's way to be user-friendly. BTW I signed up for their in person course, however it got cancelled twice in my area. I regret even messing with them.
Blueprint. Awesome company. I really like the lecture format: recorder lectures that you can view and review. In addition, they keep your account open for 2 lsat sessions--neither of the previous mentioned do this. Blueprint's materials (like powerscore's) are ample and have answers to all of the questions. In addition, Blueprint gives you online explanations to problems.
For me, Blueprint has executed the best of the three. All 3 companies do not differ much in terms of materials (though I would say BP's are the best with PS a very close second). Blueprint's approach is the most user friendly and being able to view lectures online makes the class easy to take.
That's just my opinion. I hope it's helpful.
P.S. The most important component to any course you take is doing all of the homework. In addition, I would suggest you buy LSAC's books and study those as well.