A lot of this was already covered, but here's my experience
Last year was my first MABS, and let me tell you it was the epitome of "you can't enjoy the shine without the rain". And by that I mean that I was like a kid in a candy store. After 2years of fumbling around the internet coupled with basically having never seen a great bonsai face to face since my childhood in Brooklyn, I was truly in heaven.
The masters were completely approachable, in fact, everyone was very friendly and willing to talk with me and answer anything I asked. Also, after the sort of "main stage" demonstrating would end, each master went to an adjacent room and spent a good few more hours with their demonstration material, during which time any question could be asked and the pro would answer and work, I learned from this....
Now, IF I was to be a little nitpicky it would be strictly in the intention of making a great show even better.
Allow me to explain, I did an 8 person workshop with Peter Warren, and it was basically unsuccessful and I left the workshop feeling like I just paid $150 (maybe $175?) for an approximately 8 year old jane kluis black pine and learned nothing.
But this was not Peter's fault, he was really doing his best, but how could Peter do everything and teach 8 students at the same time!? The strategy was he would basically go round robin to everyone and suggest this and that, leave for five minutes to see the other trees, then come back and take over and take over work, extremely fast obviously to finish within the time limit they gave him@. Furthermore, when I got the tree back to my house, i gave it a bit of shade, water and misted it everyday. The tree subsequently died about 1.5 weeks later. I'm NOT saying that MABS, Peter, or the place he bought it from was unreasonable. But when I contacted Peter about the tree, he said he was sorry but there was nothing he could do he just showed up and used what was given to him.
But, really, it had to have been worked on before MABS for it to up and die within 2 weeks.
Sorry for long wind post, let me digress
So, IMHO, MABS is absolutely one of the best times I had, and I'm hoping this year will be even more so. However, I would not recommend the workshop (sorry if people hate me for this, but everything else is great, not good, GREAT. See you there!