I'll start this by saying that the Eris's WiFi radio is pretty weak, but I have had no trouble with WiFi on my Eris on any ROM - until recently. Anyway, I've run Kaos through V35.1 without trouble; Nonsensikal through 7.0 without trouble; CELB through 3.2; xtrROM through 4.6 without problems; and I am now on xtrSENSE 4.6 and it's working great.
CELB is the weird one. I recently upgraded to 3.4 and WiFi has been weird - it tends to take a long time to attach to WiFi here when I come into range or turn the radio on. I am wondering if it is the new V6 of Conap's CFS kernel.
Anyway, I have a two story house with three access points, one on each floor and one in the basement, all with the same SSID but on channels 1, 6, and 11. That would be the one thing that I would check - on one of your notebooks, run an app that will do a WiFi scan of all access points to see if your neighbors are running on the same channel that you are. (There is also a phone app called WiFi Analyzer which can do the same, if you want to keep it to your phone, though I'd think that your laptop would have a stronger radio.) If they are, try changing to a different channel (you should stick to 1, 6, and 11, though you really can choose just about anything - just try to stay about 4 or 5 channels away from a neighbor's signal.) Also, if you are running in b/g/n mode, try changing to b/g only temporarily to see if that makes things any better. Lastly, you can always see if your router/access point has a firmware update available - that may help.