Having posted a plea for people to voice their feedback in a constructive manner, I feel somewhat compelled to put up my own feedback post on the topic.
First off, just a bit of background. I’ve not been a heavy D&D player, but I have had the opportunity to run and play 3.X and 4e. My primary experience with running rpgs revolve around titles like Legend of the Five Rings and the World of Darkness. That said I’m also a fan of stronger crunch games like Fantasy Craft and the HERO System.
Now then, onto my feedback:
What D&D did well:
My best experiences in D&D 3.x come from interactions with fluff-heavy settings. The Forgotten Realms and Ravenloft in particular were highlights in my experience. The fact that PCs were not constrained along a series of limited choices was something that I enjoyed. Sub-optimal character builds existed, yes, but I didn’t feel bad about playing such. My favorite character in 3.x was a Gnome Cleric of Waukeen who ended up as a cross between Jack Bauer and an Auditor.
I know that there’s a strong community in 3.x that enjoy optimization, and I’ll be willing to concede that the optimization “sub-game” is a feature and not a bug. It exists in many other systems, not just D&D.
My 4e experiences weren’t bad either. The writing of the DMG in particular was very good for a starting GM with good advice and strong support to help someone run his first game, while still having enough meat for more experienced GMs.
How D&D didn’t do well:
3.x and 4e were both victims of feature creep. Feats, Racial Abilities and Class abilities just stacked up to the point where it was daunting for many people to play. In fact, towards the tail end of their development circles, it was difficult to get new people to try the game since they felt that they couldn’t make a decent character unless they slogged through ALL the available expansions.
4e’s classes also felt rather rigid. I understood the game design direction to limit choices to smaller, meaningful ones and I appreciated that. However the smaller choices felt constraining. I’m aware that this paragraph almost directly contradicts the prior one, and I feel that perhaps it might be a good idea to find some sort of balance that could be struck.
4e also suffered from what I felt was a strange attempt to imply a setting while concealing that there was a setting. Each of the powers were given some sort of fluff, but I felt that it was out of place since most of the cosmology and metaphysics were obscured. 3.x did better here in the sense that most spells and powers were generic, and the specific fluff came in only in the context of the setting books.
Monster Stat blocks in 3.x were painful to look at. My eyes would glaze over from the sheer amount of data presented. I was immensely grateful for how 4e presented usable and easily understood stat blocks.
Other Games to Look at:
Fantasy Craft is an excellent example of a complex game with neat options. The Classes are broad enough to support multiple sorts of concepts to the point that the Scout class and the Soldier class could be an equivalent to the D&D Ranger. There are still a lot of feats, and I’ve spent hours on making a character, but the fact that it’s been limited to a single corebook (and a handful of supplements) is a great help.
Pay particular attention to the sheer number of dials and switches in Fantasy Craft’s campaign design section. Being able to scale for heroic or gritty games, and ways to tweak how magic works and other little things are all very helpful.
Life and Times of a Philippine Gamer 
Leading by example! Good stuff. The nod to Fantasy Craft was interesting. I listened in to a Gamers Haven podcast recording of the Crafty Games seminar at GenCon 2011, in which they quizzed the audience about many of the same things – asking what they’d change, what they like, are combats too long, are there too many dice rolls, etc. My impression is that they’re a small shop, so that’s relatively easy for them to do. Kudos to WotC for doing the same. Theirs is a big ship.