I did a ton of research on this before buying the HMD I chose, field of view is one of the most important things to look for, the human eye has about 100 degrees vertically and 120 degrees of horizontal of view, about 60 degrees of view is taken up by your non focal peripheral view in each direction.
40 degrees of field of view is the "sweet spot" when it comes to head mounted displays, aim for that. More is a waist, and will actually cause problems if the thing you have to focus on say... start menu, or HUD of the game you are playing is right outside your normal field of view. Lots of eyestrain and is unatural. If you want immersion, just turn off any additional light sources, it will cause your eyes to focus without much added strain and you can watch/play for longer.
resolution is important but not *that* important, I could honestly not make out pixels from that close, when the screen is 4 inches 800x600 is detectable *barely* when you get really up close with your eye. Now smoosh that resolution down to about 1.5 - 2 square inches and it becomes almost impossible to make out individual pixels.
3d is possible with any steroscopic view see 2 original displays conjoined into a binocular view. If they don't specify it's a stereoscopic view then it probally ain't really 3d. The problem with the 3d in games and stuff, you have to have 3d drivers supported by your video card manufacturer. nvidia currently is the only manufacturer with drivers that support that functionality, but they're very old and antiquated. I think the last version they had when I checked were only windows xp compatible, to get vista, 7 or heaven forbid 64 bit drivers might be damn near impossible depending on the video card. You have to match the 3d driver with the video card driver, down to the version number. Like I said, one of the most daunting tasks.
The drivers for the HMD it's self are also only xp compatible as the last time I checked. Getting 64 bit, 7 and even more unlikely, digitally signed drivers I honestly think are actually impossible from certain manufacturers. This kinda 3d head mounted display envroinment, you really need to set up a specific rig with certain model cards and hardware for it to work well. I had designed a complete system as a solution for the product I was demoing and I remember I had gone through at least 3 different target platforms before I found one that worked flawlessly, many man hours... rewarding, but lots of hard work. It's not just a "wham baam, thank you maam" project. At least not one if you want to get any decent results. That and it won't be cheap either, doesn't have to be stupid expensive, but for quality, you will pay for it.
hopefully that gives you some insight... before I sell off my HMD I'll hook it up to the pandora and take some pictures or something and try to capture a video of it in action lol
