My initial thoughts on 4E when it was first released was that it looked like a lot of fun and had a lot of potential, but lacked options. I felt a bit constrained with the limited selection of races, classes, paragon paths, etc, which is natural considering that the month before I was playing 3rd Edition with its 60+ classes and infinite feats.
I had about a hundred 3rd Edition books and supplements, each containing numerous options that invalidated other things (ie, fighter and sorcerer prestige classes), tried to patch things up (Reserve feats and Book of Nine Swords), or tried to shoehorn in yet more sub-systems which in the end probably didnt work (skill tricks, everything in Tome of Magic).
Compare that to 4th Edition, with its one book for players? Well...yeah. Kind of felt like 2nd Edition all over again. I could play a fighter, wizard, rogue, cleric, blaaah. I think mostly my issues were rooted in the fact that I'd been there and done that for over a decade. In practice, of course, everything seemed very different, new, and refreshing. For example, fighters and clerics were fun to play (I'd never played a cleric before 4E).
As a DM, adventure and monster design became a breeze. Monsters felt different from eachother. Planning adventures, to me, becamse much more about building a story instead of stat-blocks to drive that story. I felt less constrained. Other players started to step up and DM their own games. My roomie ran an adventure for another player and myself, for the first time ever, without fully reading the books, on the fly. And it worked.
I didnt care that the game didnt imply a hefty dose of immersion or simulationism. 3rd Edition might have had a larger emphasis on it, but the Craft and Profession sub-systems almost never made sense, and almost never got used in my group. I thought it was a good idea that the designers focused the game more on its purpose as opposed to trying to spread it out too thin, and in my opinion the game is better for it.
Anyway, that was my initial impression in a nutshell: 4E played very well, but didnt seem to have enough choices to reasonably sustain this fun-factor given the fact that I was playing now anywhere from 2-3 times a week.
A year later things have changed considerably.
With two Player's Handbooks, Adventurer's Vault, two power source supplements, and a campaign-specific book with not-so-campaign-specific character options pushed out, players now have a massive list of things to choose from. This doesnt even touch the breadth of choices available through Dragon.
As the year progressed, I started feeling less and less constrained. More options became available. I knew I wouldnt use much of them, but it was the fact that they were there that helped.
Making characters has never been more fun. I have a lot of things to choose from, and I dont feel like I'm making a bad choice or hamstringing my character just to mechanically justify a concept. I can make multiple iterations of the same class and they play differently, but also effective. Both Josh and myself make characters for the hell of it, and I've posted up a handful of the ones that I like the most and really want to give a shot.
Of course, making characters is faster and easier to store thanks to the Character Builder, which is the first character creation program that I've consistently used and enjoyed ever. I think that this is easily worth the cost of DDI, though more on that below.
What abou the other side of the screen?
DMs get a shit-ton of support, as well. Two books filled with monsters, two books specific to certain monsters, Manual of the Planes, and Dungeon Delve go a long way in providing advice, examples, and brand-new content for you to use. I've gotten quite a bit of mileage out of Manual of the Planes and Open Graves thus far, which is something that I could not say in past editions (except perhaps when I ran Planescape, but even that was mostly constrained to Sigil).
I was initially skeptical about DDI when I heard they were doing an online, digital bit. I too enjoyed getting magazines in the mail, but honestly I never really used them. Having given DDI a shot and seen what they have to offer, its worth it. Its handy that DDI content gets added to CB, which just increases the chance that I'll notice and use it, which is something I couldnt say for 99% of the stuff featured with Paizo had the reins.
All in all, its been a very good year. The game has grown quite a bit, and I'm looking forward to another year. My only regret is that I dont have enough time to run all the campaigns that I want to run.