PS I don't mean to pick on Linksys, it's just that they're the ones I'm most familiar with. Overall the fails seemed to be in proportion to market share although every one had its particular problems.
I'll pick on Linksys. Products which overheat, have bug-ridden firmware, and an utter lack of quality control do not belong on the market.
Remember that small workgroup switch you'll often find stuffed behind a file cabinet in small office environments? It's the one whose existence you only become aware of when one or more people suddenly cannot connect to the network. A brief power outage / moon phase / random fart caused that switch to quit receiving packets, requiring a power cycle. Yep - Linksys switches are infamous for this.
The WRT600N wireless router was a decent piece of hardware, but suffered greatly due to substandard firmware. Not only was the web interface prone to random acts of stupidity like refusing to clear a field (DNS entry #3 was one such field which could not be cleared without a complete factory reset), but wireless connections to this router would become inceasingly unreliable over an approximate period of 24 hours, at which point the router would drop connections completely.
Then there's the WRT120N. This router shipped with a slight flaw which prevented Intel 2200 wireless cards (Centrino) using the Intel drivers for Windows from obtaining a connection. How did QA miss that little bug?
Seeing the quality of products Cisco has shipped under the Linksys brand makes me wary of using Cisco-branded products as well. Any company which could put such badly made and tested products on the market doesn't need my business.