I have to admit that I did hate it. In fact it stopped me from picking up what is now my favorite game (Everstone: Blood Legacy)
We had a DM who tried to play BESM d20 over and over (well 3 sessions). Just like most people agree. The armor is broken. The Combat Skills are broken, and everything is so vague that it took our DM forever to make a seting, villians and everything else (probably why he made us sit through 3 sucky sessions). I agree with the other posts that state that the makers didn't even know how d20 worked.
But the cool thing is they let a second party make a game with it that understood d20 and fixed all the bugs. One of our group picked up Everstone (which uses a d20 system like BESM d20, but with everything fixed) and let me tell you he had one hell of a time trying to get us to try it out. We finally gave in and our group hasn't quite playing. He handed out some architypes he got off their webpage or we would never have played.
All the cool stuff, like complete customizable character classes, is all there. They took out the Combat Skill crap, kept the Armor reduction stuff but toned it down to be playable. And created detailed attributes which cleared up all the guess work. We tried to use the BESM d20 stuff with it, but gave up. The Everstone book is a complete rule book and you don't need it anyway.
Again we tried putting other d20 classes and monsters into the BESM game, we had a few good laughs.
Not to mention their huge screw up with the BESM d20 revised. They accidentily reprinted the first book and tried to resale it. OOOOOPS!
Kind of wish they would give the BESM d20 to somebody else who understood how d20 works.
For pure psi-fi I find that Trinity and Abberant are the best.