JackMDS - there's a major difference between the various VPN endpoint routers -- some have a hardware crypto chip in them and some don't. That's an order of magnitude performance difference, and interestingly enough it doesn't totally correlate with the device's cost. The BEFVP41 is about $100 now and has a HiFn 7901 in it and a generous tunnel limit -- it seems to be the current winner.
DeRusto - at the low-cost end, the main difference is in the firmware and the company behind it. Heck, you crack most of them open and it's the same chip inside running the show (two Conexant chips dominate the low-end SOHO router space).
Linksys has the most features, probably the biggest user following, and pretty good community support if you know where to look (apparently their phone/email support is, uh, industry standard). But they also seem to have the most bugs and their AC adapter bricks aren't very reliable (tend to die after about a year). Linksys is definitely in the love 'em or hate 'em category. (Note that the "Linksys Network Everywhere" boxes, while cheaper, lack firmware features vs. the normal Linksys boxes). The Linksys SOHO router most people seem to get is the BEFSX41.
D-Link has almost as many features and a bit more reliability. The DI-604 seems to be the one most people get.
SMC has fewer features, and used to be considered reliable but a lot of people seem to be having problems with them lately. 7004ABR is most common.
Netgear-low-end and Speedstream are more basic, but more reliable. Netgear-higher-end and ZyXEL are more expensive but I've heard from a lot of people that they're good on features and reliability. Hawking are cheap and I have no real information about them. There are other manufacturers out there, but they're a lot less common.
Roughly all the time, Linksys and/or D-Link SOHO routers can be had for deals after mail in rebate. I'd grab one on whatever deal you like best.
When JackMDS says "special applications" - you might not think you need it now, but you will. This is a huge problem with PAT/NAT devices -- some applications don't work with them well and need special magic in the device to work around that -- and in general you will be happier having more features that let you try to work around these problems.