I recently switched from Comcast's cable modem service to Verizon's FIOS -- I get about 3x the download and 4x the upload speeds, and I save about $10 a month. Overall, I've been thrilled with the switch, other than with the router that Verizon provided. It's an ActionTec, and it's got perhaps the worst web-based GUI for a router that I've ever seen. Setting up port forwarding, for instance, is a real pain.
Last weekend, I wanted to set up an externally-accessible web cam, but despite what seemed like the proper setup in the ActionTec, I had no luck. So I pulled the ActionTec and installed my original Linksys BEFSR-41. I entered the port forwarding info for the web cam, and it was online without any issues at all.
A couple days later, I noticed that my FIOS connection wasn't feeling quite so speedy -- I'm supposed to be able to get up to 15Mbps of download speed, but the SpeakEasy.net speed test was reporting only around 5Mbps. After some searching, I found the answer. Apparently, this is a limitation of the Linksys router I own -- my BEFSR-41 is an older "V2" model, and the WAN port is limited to (I don't fully understand this part) 10Mbps duplex, which means 5Mbps download speed. The newer V4 model of the BEFSR-41 has no such limitation. When I put the ActionTec back online, the speed tests returned to their normal values.
And while this was only an issue for a couple of days, it's actually a bit worse than that. For the last couple of years, I was on the Comcast "high speed" cable plan, which theoretically gave me 8Mbps download speeds, but I recall never getting anywhere near that ... and now I know why. Guess that was $6 a month that I didn't need to spend!
The moral of the story is that today's high-speed net connections may have outpaced your router's capabilities -- especially if, as with mine, it's an older model. Visit one of the speed test sites and make sure you're getting everything you're paying for. Compare your speeds when connected through your router and when you connect your Mac directly to the cable modem; they should be nearly identical.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061228072537434