Well, the other prequel he wrote outside of the series, New Spring, was quite good, so I wouldn't mind more books like that if they focus on the right people(Lan is always a winner). The relationship between Tuon and Mat is not something I'd want to read a whole book about though, as I find the parts with them fairly boring already.
Anything containing Egwene and that subplot or Tuon and that subplot is uninteresting to me, the rest is great. Unfortunately, book 10 was all about those two subplots, so it was the worst book so far in my opinion. Luckily he's not focusing on them anymore though, and book 11 really brought the series back on track.