I first went to the seminar about 2 years in. It was great. Granted, I already had heard all the "advice" and many of the anecdotes, but I still got a huge amount out of the charge it gave me. Just being in a room for 2 days with 100-200 (or so I guess) people who are all excited about this was a real boost for me. I spent a lot of time during David's lectures actually doing a mind dump -- things he said would remind me of things, etc.
Tip: take a big pile of note cards so you can capture all the things that will come pouring out of you. I went through an entire half inch thick 3x5 note pad with all the things that percolated during those two days - new things to try, old things remembered, etc. (And that was AFTER I completely used up my Palm battery!)
I'll probably go to the seminar again in another year. It was really great. (Plus, if you happen to be in LA, he holds it in a room on the top floor of a hotel with floor to ceiling windows on both sides giving a view of the entire Los Angeles harbor and coastline . . . simply stunning. Even if the lecture had been utterly worthless, it would have been worth the money to get to spend two days in that environment.)
So, yes, you should go to the class, imho.
Taxgeek