Depends on what you mean by "low end".
Using it to remote control a 600 mhz Pentium 3 Dell GX110 is a laggy experience. A 1 ghz Athlon XP is better, but still noticeable. Once you start getting into more modern stuff (late Pentium 4s on up), the host PC handles the additional load no problem. On my Atom D525 media server, it's nearly as fast as Remote Desktop. (If at all possible I actually just use RDP over TeamViewer's VPN.
)
Remote console is no good for gaming. It's fine for showing off ("look my iPhone runs Crysis!"), but it's not something you'll be entirely happy with except for things like LucasArts adventures and Minesweeper. (Plus it will look like crap at the "optimize speed" setting.
However, playing LAN-mutliplayer-only games over TeamViewer VPN
does work just fine provided both parties are running the game locally.
If you have a second computer on the network, you can see how TeamViewer's raw speed compares to how badly your upload speed gimps it. Enable LAN logins in the Options window, and connect to that PC using its network name (not the long description name, the short WINS name like "DELL7PF96G"). This directly connects the two machines. Play with it for a bit, then disconnect and reconnect using the 9 digit ID number. This will make the data go through TeamViewer's system. You'll probably notice a bit of a difference.
At minimum resolution and quality, you
might get 10 FPS if your network connection is up to the task.