Well this thread has been dead for a few days. Got a 32GB one a few days ago. Actually bought it from EB (Electronics Boutique). They literally only just got them in the day I bought it as they have never carried iPods before. Since I had $330 in credit from game trade ins, it was a no brainer for me. I actually wanted to get the 64GB but apparently they don't stock them and won't be able to order them in. The funny thing is that they had piles of cases as well which were all for the 2G/3G which of course don't fit. I pointed that out and the guy just facepalmed himself and said "I know".
Anyway, been playing around with it for a few days. Very impressed at the moment and in my mind, a substantial upgrade even from the 3G version. Firstly, the retina display is a thing of beauty and completely destroys the old 3G screen in every way. Think SD to HD and you're getting close to the difference. The depth in the picture is incredible and pretty close to looking out of a window. Blacks and color depth is also on another level, and very obvious when both screens are side by side. Viewing angles are merely okay, but who really cares on a screen this size? The bitching about this from some people is unwarranted IMO. Unfortunately I don't have an iPhone 4 so no comparison to that from me.
Some people have said the size reduction was unnecessary but personally I think its very welcome. Compared to the 3G it is slightly taller, but not as wide or thick. Feels very nice in the hand and the reduced bulk is definitely noticeable. I wish they would ditch the chrome backing already. As with every other model, it'll scratch within 5 seconds. Now to the back camera. Yes, its not very good. During the day with perfect lighting conditions its fine, decent in fact. At night time its close to useless, don't even bother. One good thing I'll say it that it takes the image almost instantly. Great for random snaps in that regard. Haven't tried much video recording yet but I took a 1 minute clip during the day and it was solid.
On the software side it runs extremely smooth now. With the 4.1 OS update and the new A4 processor, lag is virtually non existant. Games that have been upgraded fro the Retina display look fantastic. Though its not a game, Epic Citadel will certainly impress you especially with the upgraded resolution. I haven't tried any games that use the Gyroscope but from what I've read its very good.
Sound quality wise I like it. This is coming from a guy who already thought the 3G sounded nice. For comparisons sake, they sound pretty similar except that 4G is slightly warmer. This makes it an even better match for the M50s. For anyone wondering, these two have a great synergy. I never use EQ but for the purposes of this review I did. From memory the EQ used on Apple products has always introduced horrible distortion. No longer the case. I don't think this has been a hardware improvement though, as the 3G also doesn't distort anymore. I'm guessing the new OS has fixed it. The built in speaker is a bit louder now. On the 3G, listening to podcasts on the speaker in a noisy environment was always difficult, even at full volume. Now I can comfortably hear it without straining.
All in all a great update to the Touch range. For anyone having doubts, I would fully recommend it, especially if you were happy with the old models but wanted an upgrade. For people who want it solely for music listening, I would still say its a good purchase but overpriced obviously. If you didn't like the SQ before you probably still won't like it, the difference isn't massive.