I just got a Zoom 5341 modem to replace a very sketchy old Motorola model and so far it seems to work fine.
However, the Comcast self-install switch process was not seamless. After you plug your new modem in the process starts fine, capturing your session and prompting you for your account. However at the next step it prompts you to download the Windows or Mac only client, directing you to an address http://cdn/....
It is at this point you can get stuck if you're behind a Netgear router (I have a WNDR3700) and probably others. The simple problem is that, for whatever reason, the factory firmware in this router does not pass on the domain search suffix through its inbuilt DHCP client. Without that, cdn doesn't resolve to anything, so you can't download the self-help tool and you're effectively stuck at a "can not find this page" screen. If you google at this point you can find many people who have hit this problem, and various information from erroneous suggestions that you've been hacked (?) to most people just giving up and moving into Comcast phone support hell.
Assuming you now don't have internet access, you can complete the process with a quick swizzle. Somebody might be able to correct me on this, but I don't think you want to run the self-install tool from an actual computer plugged directly into the modem if you have a router in the picture, because the wrong MAC address will get registered. So, your best solution is to turn everything off, plug your computer directly into the modem, turn it on, get an address, download the tool, turn everything off, plug the router back-in to the modem and then run the self install tool. At this point, everything just worked fine for me.
Netgear should probably fix this by correctly passing through the domain search suffixes in their routers. Comcast should probably fix this by doing some sort of geo-ip lookup to give clients a fully-qualified address in that webpage to download the tool even if their router is broken (or really, does downloading that file really require a content-delivery network?). You can probably fix this by running Openwrt on your router before you start.
Otherwise, the Zoom modem and the Netgear WNDR3700 seem to make a very nice combination which I would reccommend.