The main difference as far as I'm aware is that it's wireless and doesn't require a computer. It seems there are a few others have already hit the wireless mark. Not needing a computer is a big deal, but doesn't affect me personally (I only use it at home; I still want wireless though).

It's a pretty big difference. The issue is that you're basically going to need on-board computing in order to compensate for the lower bitrate of wirelessness, a problem that gets worse as the resolution increase. You need to do warping on the headset itself (as well as sophisticated compression) or you'll have motion sickness. So while it's possible to hack wirelessness on some of the other headsets currently, that becomes less and less feasible as resolution improves. Also, not requiring a computer is a bigger advantage than you might think. I also use my Quest only at home, but I'm able to use it anywhere in my house (wireless video direct to a headset without on-board computing uses 60GHz WiGig, and therefore is basically line-of-sight and very short distance only) and regardless of what the main computer is being used for. (Also, requiring a gaming PC for operations easily doubles the cost of the solution.) A separate wireless adapter (WiGig) on the PC also adds cost and is bulkier than the lower bandwidth Wifi connection you can use if you have on-board computing.

An example of how it's qualitatively different is I use it outside (at dusk). That's not really practical with other devices, and it's a completely different experience.