I'm not quite sure what you mean by that. If you mean speed-wise, I managed to get it working (just!) on an 800MHz machine, but I'd say 1.2GHz minimum.
If you are talking in terms of the control system, I much prefer the keyboard and mouse system as I am used to it. If you are used to control pads, then you can buy one and use it in conjunction with GTA.
It depends what the other machines are doing. I've got 3 on my LAN, and I find no problems at all if I play a game whilst the other 2 are surfing the net. However, if they were also playing games / downloading large files, this might affect it somewhat.
ASE is a 21-day trial version, unfortunately. However, you can obtain lists here:
http://www.mtaservers.com/index.php?q=list
http://www.mtavc.com/servers.php
I recall one of the developers once saying that Gamespy had expressed an interest, so presumably future versions of MTA will be supported by Gamespy Arcade.
I'm not really bothered by cheaters - if they kill me and I can't kill them, I just respawn and don't bother picking a fight with them again. Also, it can be hard to tell if people actually are cheating (due to some small bugs in places), so I usually give them the benefit of the doubt.
I think people tend to exaggerate the number of cheaters (some noobs cry cheater at the slightest thing), but there aren't cheaters on EVERY server, so you can just find another one.