. . . putting yourself in the shoes of someone who will be doing recreational diving with $400 to $600 to spend on a dive computer. To keep within that budget, what do you get as your first dive computer and what options do you forego given that budget?
I initially bought a Suunto Vytec - wrist-mounted, nitrox capable, air-integration capable, 3 gas switching, PC interface available. If I had it to do over again, as a first computer, I would buy the same thing.
I definitely prefer a wrsit-mounted unit. I liked the Vytec display size - I could read it underwater. The computer 'grew' with me, as I started using nitrox, as I moved to technical diving and the use of multiple deco gases, as I added a transmitter (not to replace my SPG by any means, but as an element of convenience u/w). I could change the battery myself (although not usually recommended). The only limitations - not much light in the display in dark/low light conditions. That wasn't a big deal.
I have used Niteks (the He), the Liquivision X1, and a Helo2. In fact, I sold the Vytec to be able to afford a Helo2, which I wanted as a back-up unit during trimix dives. Of all of them, I prefer the Nitek the least, primarily because the screen is hard to read u/w. I prefer the X1 the most, primarily because the screen is SO easy to read, and the use of 'tapping' to change screens is SO much easier than buttons. (But, as TS&M mentioned, not in your target price range.) I thought I would like the Helo2 a little more than the Vytec, but that hasn't been the case. Good computer, gives me trimix capability, not as easy for me to read as the Vytec for some reason.