I would not recommend the DIR-655 as it comes out of the box. I had issues for the last two weeks that I've had it with the 1.32NA firmware. My internet connection would be unavailable as well as the router's GUI interface every few minutes. EXTREMELY frustrating.
However, I believe this was due to the SecureSpot feature.
I HIGHLY recommend the DIR-655 if you roll back the firmware to version 1.21 (no secure spot). It isn't possible to *directly* do this, but this link can show you how:
http://www.ispgeeks.com/wild/modules.php?name=Forums&file=viewtopic&t=4229&mode=&order=0&thold=0
After I did this, the router is rock solid. The speed is very peppy, the router is always highly responsive now. I'm proud to say it works better than my 5 year old trusty Linksys WRT54G router. This is how I expected it to work out of the box, but the 1.32NA firmware is garbage.
Best part of this router? Two xboxes on Xbox Live at the same time, and OPEN NAT! Thank you QoS! This was the main reason I bought the router, for its great compatibility with Xbox Live. No freaking port forwarding or DMZ settings to fiddle with.
It is worth mentioning though, you will not get the full 300Mbps wireless speeds with a Mac. I have a Mac, and Mac's do not support 300 Mbps wireless over the 2.4 Ghz band due to lack of support for 40 Mhz wide channels. The Mac would get these speeds in the 5 Ghz band, but the DIR-655 doesn't do wireless N over 5 Ghz. Not a big deal for me though. My internet is 10 to 20 Mbps, so I wouldn't see any benefit with 300Mbps wireless speed. I'm getting around 130 Mbps most of the time, and that's overkill ; )
P.S. The USB Shareport on the DIR-655 works with only one computer using it at a time. If you were to plug an external HDD into it, only one computer can connect to it. It won't turn your external HDD into a network storage device, which is kind of sad...... Oh well, not a deal breaker for me either. Hope this is helpful!