The VFX-1 is a nice device for the money. I bought my headset brand new for 600 hundred dollars from Computers and More. I would recommend that if you are considering buying one that you go to E-bay and take a look. Normally you can pick one up for around 300 dollars.
Right off the bat, you have to have a video card that has a 100 percent compatible Vesa Connector. I have found that about the highest megabyte card you can get is an 8. A company called Mindflux used to make a linkbox, so that you could use it with all those higher ended video cards, but are a pain to deal with. The chances of you getting a hold of one of the box's is slim to none.
Secondly, you must have an open ISA port and an available IRQ for the headsets interface board. This board can be a pain especially along with the VESA connector. You have to pick and choose between a video card that will work with the VFX or a video card that will give you graphics like those of the Voodoo kind.
Another item that is worth mentioning is that the VFX will have different performance ratings with different systems. One application that will work great on one machine might not work at all on another machine. This can become irritating.
Despite all of that though, I do believe the VFX-1 is worth the time and effort. It gives a pretty good immersive experience and works awesome with Quake in 3D. I would give the Headset a thumbs up.
One thing to condsider is a setup like the Virtual I/O glasses, or the Glasstron. They require a VGA to NTSC converter but do not depend on your entirely on your graphics card(The VESA connector). You can have a Voodoo 3 card and those of that caliper. They also do not need the IRQ or a free expansion slot. They do however lack the Headtracking that the VFX includes. Seperate headtracking like that of Intratraxx is available though.
* Here is an electronic copy of the VFX1 Users Manual. This is a 5 meg file.