Speaking only for myself, I initially thought 3.5 was a really great idea. In practice, however, I became pretty pissed-off about the it, and suffered from
point-five burn out bad enough drive me out of D&D for a couple of years.
Understandable. However, I think the big problems with 3.5 weren't so much the concept, but rather that it was put out too soon, and made a lot of minor changes to things that didn't really need fixed (I recall a number of complaints about it being "Andy Collins' house rules"). It also didn't help that a lot of the fixes either didn't really fix the underlying problem (as with polymorph), or in some cases were actually worse than what they replaced (weapon sizes - good concept, but far too fiddly in implementation).
The risk with fractional maintenance releases like 3.5 is managing the compatibility dilemma; too many fixes breaks effective compatibility, too few negates the value of repurchasing books you already own.
Pathfinder, I'm looking at you!
Indeed.
If skill challenges turn out to be the only major redesign...
I really suspect they won't be. However, I also think we probably don't know what areas will need the work done. 4e has only been out for 8 months, after all. According to WotC's own expectations, that should be just enough time for the first campaigns to have run from 1st to 30th level, and I bet very few groups have done anything like that.
Anyway, even now we know of some other areas that may not
require redseign, but could certainly use some work:
- Grinding combats (probably the biggest one, actually - the combats do work as written, but they could certainly be a whole lot better)
- Solo monsters (as mentioned by the OP)
- Stealth
(None of this is surprising, btw, and not even something WotC should necessarily be blamed for. The game has undergone a total redesign, and so it was inevitable that there would be problems. It's just that, in light of that, I think a 4.5e would be justified. But then, I'm not entirely convinced they won't do one anyway... they'll just call it 5e.)