Others say...

"Nice spec. Lousy implementation."
I just can't recommend this router to anyone at the moment, esp. with some fundamental problems below:
1. DHCP - If you have a dedicated DHCP server somewhere on the network, then forget about this router. The darn thing would still assign IPs even if you disable the DHCP function. It'd also send DHCPNACK with DHCP diabled.
2. DHCP again - If you assign a DHCP range and assign them as static entries. It'd still assign those IPs to other machines.
3. DDNS - Obviously the router doesn't keep track of the WAN IP changes and if you save the configuration a few times, it'd try to update the IP on the dynamic DNS server multiple times, causing the custom domain to be banned.
4. Tech support - Not exactly the router's problem but if you have a support person who'd recommend connecting a cable modem to the LAN port to get around the DHCP problem, you're just not going to trust their tech support anymore.

"A great router now that it's (kind of) affordable"
I have been using this router for about a week. Setup was easy enough, even though I skipped the CD and just dove into the settings manually. The manual gives enough of a description of the settings to make your way around. One thing to note when changing router settings. Save your settings on each tab before you go to the next one. Otherwise, you lose your work. You can't just change all the settings and do one save action.

I teamed this router with the linksys WUSB600N USB adapter using only the N band. Speed has been very good with throughput on my DSL connection benchmarking the same whether wireless or wired. Setup of the USB adapter was very easy too.

The only hick-up I've had was I recently upgraded my DSL speed. That scrambled the router's eggs. I suddenly lost any ability to connect to the net via the router (wirelessly or wired) even though all the settings were correct. Resetting the router and re-changing all the settings again fixed the problem.

The button on the top of the router is still useless until Linksys enables it via a firmware update. It's supposed to make connecting a wireless adapter to the router a one button affair.

Overall, I've been pleased and these two devices were easy to set up and work well together.

"Easy setup - Very dissapointing Wireless performance"
I purchased this unit because I gave my daughter the D-link DIR 655 unit I had (which worked extremely well). Since I needed a new unit I decided to give the WRT600N a try. Everything started very well. The installation was easy and intuitive. Networking is set and you're up and running in a few minutes, or so you thought...
My wife's PC is connected to the router via the 1GB Ethernet and naturally this connection is very fast. I have a ReadyNAS network storage device that is also connected to the router via a 1GB Ethernet connection. This is our central storage where we keep our files (movies, music, documents, e-mail, etc.). This connection is also very fast. Working on my wife's PC is fast and easy (I have a 7Mb ADSL internet connection from Qwest).
The wireless network is another story altogether. My wireless network has many devices connected to it - PS3, Squeezebox, my PC, my laptop and my wife's laptop. I set it up with WAP2 security. There are no walls to speak of between those devices as we have a large open space between our leaving room and office. My PC is 10 feet away from the router, the PS3 and Sqeezebox are 20f away... As it turns out, the WRT600N router is horrible at supporting streaming media over it's wireless network, period. The performance is choppy, inconsistent and gets worse as time goes by, so much so, that I have to reboot the router periodically. It is worse then the original linksys router I had before I switched to D-link. It is really bad. Absolutely no comparison with the DIR 655. So guess what I am doing? My experiment is over and I am getting another D-link DIR 655 device. The DIR 655 performs significantly better (as rated by all professional reviews I read on the net) and does not have any of the side-effects I described above.

"good while it lasted"
Worked fine for a week, was unstable for another week, and then failed completely.
I set it up while wired and had no problems either wired or wireless until the second week.

"Difficult to set up and inconsistent with other routers made by Linksys"
First thing I have to say is that the network storage feature does not work at all. The first time you set it up it works and after that it's anybody's guess. I just forgot it is there and use it as I would any other wireless router.

I have experience as a network administrator and had a hard time making it work the way I wanted to, and that is with the understanding of what every little switch featured on this thing does. I cannot imagine someone less knowledgeable dealing with these inconsistencies!

The Setup wizard works well only when you follow every step literally. Even after using the setup wizard you should power cycle your modem/DSL and router to be able to see the internet.

You will definitely need dual band wireless n adapters to get the best and speediest connection. Some of the default settings won't let you get the best connection if you have Linksys adapters, for example the "frame burst" setting on each band.

Once everything is working right it is a great router and a very safe one, albeit some disconnects that happen once in a while, which apparently happen in all wireless connections. Linksys should not be faulted for that.