LTE is a non-factor for me, as it is for just about the entire world except the US. But sure, if that's the only way you can get decent data speeds (from what I understand 3G sucks pretty bad in the US) I understand that it's an important omission.
The lack of an SD slot doesn't really bother me either. I'm doing just fine with the 16 GB of storage on my GNex. For music I use Google Music (I tricked Google into letting me use it by signing up via a US proxy), and only keep the stuff I'm most likely to listen to available for offline access (plus whatever it automatically caches). I just don't need my entire music library available on the phone at all times. I rarely keep any movies or TV shows on the phone, and when I do it's never a significant amount. Pictures and videos I take using the phone are automatically uploaded to both G+ and Dropbox, so I can clean them out of the phone every now and then without losing anything. That leaves games, and by keeping a healthy balance of a bunch of smaller casual and a few larger "premium" games installed I really run no serious risk of running out of space.
The camera probably won't be the best thing ever, but it should be decent enough. It's definitely vastly superior to the GNex camera, which is pretty bad in all but optimal lighting conditions. It might not be quite as good as the SGS3 camera, but is that really gonna be the deciding factor? Not to me.
When it comes to buttons I've completely embraced the future of on-screen buttons. Yes, they take up some screen space that could otherwise have been used for content, but other than that they are superior to hardware keys in pretty much every way.
And then there's the most important point of all: The pure Android experience the way Google intended it, with updates within days of a new version being completed rather than after several months. I've become too used to that to switch to a phone where I know I'd have to sit waiting for months to get the latest and greatest Android features. How many people who bought a nice phone not too long ago are still on a pre-JB version (or even pre-ICS)? Most of them. I've been on JB since July thanks to having a Nexus, and am now on 4.1.2 (and will soon be on 4.2, regardless of whether I get an N4 or keep my GNex). That's something I simply won't give up. Unless something drastically changes with how OEMs treat their software and updates, I can't see myself ever getting a non-Nexus Android phone again.
So no, I personally would never even consider getting an SGS3 over an N4.
