AbdulAlhazred
Legend
Except for badly written or edited publications, I've enjoyed 4th Ed. The thing that has bothered me most has been the uneven release of materials. We have Dragonborn and Tiefling splatbooks, but nothing for other races. They kept releasing books with new races and classes, but half the time (esp Heroes of Shadow) failed to ever support them with magic items, feats, or other build options (unless you cough up for the DDI subscription, and then a lot of the material is fan submission rather than WotC). They kept throwing out new power sources, and then pretty much abandoning them for yet newer ones rather than supporting/fixing what was already 1/2 donkey'edly done.
And as far as converting characters from one edition to another, WHY? Why would you even try? This is a new game. Make a new character. Make a new story. 4th Ed was such a drastic change (and improvement) over the previous mechanics for balancing classes and evening them out, that trying to port something else that wasn't even designed to fit is like getting upset when the square peg won't fit into the round hole.
Well, we goth enjoyed it. Honestly I didn't find the 4e materials all that uneven at all. My comparison is mostly 1e and 2e stuff, which could be all over the map quality-wise, and not 3.5, so maybe there was a pinnacle of quality that I missed in there

They didn't keep throwing out new things. In fact the PHB1 lists all the power sources that would ever exist in the game. If anything they CUT BACK by removing the concept of a 'ki' source and relegating the Shadow (and somewhat the Primordial/Elemental) power sources to secondary status. I know a lot of people are all down on Heroes of Shadow, but I thought it was highly flavorful and quite cool. It wasn't "half-donkeyed" at all, except maybe the Binder. Shadow PCs and Elemental PCs have somewhat less support, sure, but they have as much as other classes had a year in. I don't think it is fair to call that material bad because WotC has the (IMHO bad) idea to stop supplying support for 4e entirely. I'd just point out that they also had every plan to make splat books to support the other classes and more race books, etc, but apparently they weren't lucrative enough, so I'd guess people weren't that interested. PERSONALLY I thought the race books were reaching. The other stuff however was all pretty good. Nothing is flawless but I thought overall the quality of material put out for 4e was and is excellent. The production values are certainly uniformly high, etc.
If there's a blot on that it was the HPE series of modules. They suited the nature of the game poorly for the most part. There were some nice ideas in some of them and I know people that built fun adventures out of them, but out of the book they were mostly pretty dismal play experiences that tried to shoehorn a largely dungeon-crawling mode of play into a game that as Pemerton has explained is much better suited to a different style.