Switching to 4th ed very happily, though my players are not so sure, as #1 is a die hard wizard lover (I am too, though, lol), and #2 isn't has no Internet so hasn't been able ot keep up with all the changes.
Several reasons:
1) I'm ill, 3.5 is too much damned stress, stress is very bad for me. 3.5 is overly complex and pestiferous to make NPcs etc, compared ot 1st and 2nd ed where I'd easily make up NPCs at will. I DM to have
fun, not put up with all that hassle, gah!
2) High level play is VASTLY over complex in 3.5, we spend more time figuring out rules and counter rolls, than having fun. Player #2 was happy to hear "confirm for critical" rolls are gone in 4th ed, waste of game time.
I think combining/reducing skills is a thing that 3.5 players should consider to improve their games: ie replacing Spot and Search with Perception, etc

4th ed skill list is much better, though maybe add int modifier as NON-combat skills, ie Profession, Craft etc.
3) magic items are too vital and too abundant in 3.5 without them, most characters (melee for sure) are absolute gimps, that is not good! non-casters having to carry around a "golf bag" of weapons ot stay effective, while a wizard can use an alternate attack form to bypass DR etc. That ain't right. Items = fun, not mechanic tool box.
Playing D&D Online let me see how...bad, that is, ugh. Was sheer hassle and a waste of time, effort and inventory.
4th ed handles such things better by having damage/effect come form powers, mostly, and things like "incorporeal" creatures take 1/2 damage, thus removing wasted time at game table rolling ot miss...miss..miss....
Lot 3.5 should take form 4th, to make it more fun, IMHO.
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My biggest dislike of 4th ed is messing with the comsology and backstory, I'm not happy with in some parts.
"shadowfell" and "feywild" work brilliantly (especially in my homebrew setting), but eliminating the Great Wheel completely, and messing with some things (like driders, and Lawful and Chaoptic as more than mere alignments, but major Powers) is plain wrong.
I agree with parts of the reason for problems with the Great Wheel and a need for change, however, removing some of the important parts, like say, Mechanus and thus, modrons, clashes hard with previous established lore: those kind of things were vital to D&D's millieu in toto.
Example: in 4th ed Inevitables are now "peculiar" contracted planar mercenaries, eh?! Having them as the arbiters of Cosmic Laws was much better.
On the whole though, 4th ed is great improvement. 3.5 is great simulation, but the complexity is too much for most DMs I know to enjoy, and please note this: most folk in the world are
not "ENworld uber enthusiast gamers"

Not a sleight at all, most folk here are deeply passionate and usually skilled....cream of the crop, so not a good basis to set such things against, really.
Most folkI talk to do HATED 3.5 DMing, that's not good for D&D at all.
Plenty of lazy players out there don't care how much hard work/grief DM's get...plenty of players simply don't have much time to play, etc.
Each hour of D&Ding should be 90% fun, 10% mechanics!! Not the other way around.
*hugs his old Fiend Folio*
