Its got plenty of bandwidth for most internet delivered video purposes, without hogging your entire house's bandwidth. Theoretically it could pipe full Blu-Ray streams across your home network though YMMV
I've had an old Linksys WRT54G for years running DD-WRT and thats the reason I'm upgrading.
Further qualification: Dual band models. Run separate channels on 2.4 and 5 GHz. Assuming you have upstream bandwidth and/or local traffic to warrant it. Also, 5 GHz may get you away from interference from neighbors' older equipment (router, or crap-leaky cordless phone or whatever else is noising up the 2.4 band).
(Be careful, though; some equipment has limited support for dual band operation, which you only learn from hard to find fine print or third party online sources. E.g. Only one band at a time. Or degrading all connections to G if any of them are G. Or effective throttling due to an under-powered processor. As a couple of examples I encountered a year or a bit more ago while helping someone buy one.)
As for me, still on my 54GL -- good enough for my limited needs at home.
Could somebody give me a reason why I should?
It runs open-wrt, it does NAT, it does packet switching, it powers on in a few seconds.
What else could your router possibly do for you?
Routers are refrigerators, if they're still keeping things cool, don't touch them.