My last wifi broadband ADSL router (a Belkin model) recently failed - the broadband speeds became slower and slower until they were practically zero!
When looking at current Wireless N ADSL Routers I found that I would have to make too many compromises if I purchased a combined solution. Therefore, I looked for a solution which split the ADSL box from the wireless router, so that if either part failed, or if either part needed upgrading, I can do so while choosing the "best of breed".
I recently had a Belkin Wifi Max ADSL Router (which lasted only 2 years) which could only achieve about 5Mb download speeds, whereas with the TP-Link TD-8840T, I can achieve well over 6Mb speeds.
I use this router in conjunction with the Asus RT-N66U Wireless N Router. I think that this is the BEST setup, at present, while the newer AC Routers become more widely available.
UPDATED REVIEW 02/05/2013
This modem failed and would no longer synch after only 6 months. I installed the BT Home hub 3 I have which worked immediately so confirmed that the TP-Link had failed. I'm also getting about another 0.5 to 1Mb more speed from the home hub.