I've been playing City of Heroes in Linux and it seems to run quite well. So here's how I got it working, in case there are any others out there who don't use Windows but want to play the game.
There's an emulator (well not really an emulator, more like a runtime library maybe?) called Wine that allows Linux to execute _some_ Win32 code. In order to run City of Heroes, you must use a version of Wine called Cedega (formerly WineX). Cedega was forked from the main emulator some time ago by the people at Transgaming (which caused no end of grief in the free software community, but that's a discussion for another time) and is now a commercial program. You can either buy WineX from Transgaming.com (which you may not want to do if you are a GPL purist, as Transgaming kinda "stole" the original BSD licensed code in the first place), or if you are feeling adventurous, you can compile it from CVS without paying, using the instructions here:
http://www.linux-gamers.net/modules/...p?articleid=45
After installing Cedega (at the time of this writing, version 4.0.1), you should be able to mount the CoH CDs and install them via "cedega /cdrom/setup.exe" or whatever your CD mount point is. Just remember not to cd into the cdrom mount point, or you won't be able to unmount CD1 when you need to insert CD2.
After installation, you can just cd into your installation directory (mine is ~/COH/), and run the game via "cedega CohUpdater.exe".
There are some issues, however, which I will enumerate below:
1). (May only apply to nVidia cards) Run your X server in 24 bits. 16 bit color causes the game to run _very_ slowly.
2). (May only apply to nVidia cards) If the cursor appears as a black rectangle, maybe with some junk underneath, set the following options in the "Device" section of your XFree86 configuration file:
Option "SWCursor" "true"
Option "HWCursor" "false"
After doing this, the cursor will only be visible when you move the mouse, will flicker, and will sometimes produce artifacts. A minor annoyance.
3). Make sure you set the VideoRam and AGPVertexRam options in the [x11drv] section of ~/.transgaming/config to the proper values. Otherwise, not all of the RAM on your video card will be used properly. And also make sure you actually have OpenGL turned on from within XFree86 configuration and that it is working, using the glxinfo program (I think there are instructions in the Cedega documentation).
4). Make sure that cedega reports itself as being Windows 2000, either with a commandline option or a section for CoH in the ~/.transgaming/config file.
5). The license agreement is not displayed in the updater, nor are the release notes, because it tries to use an embedded IE window. The URL is, however, printed to stdout, so you can still get the documents by pasting the URL into mozilla. Which I highly recommend doing, because you have to read the license agreement to legally play the game, afaik, at least if you live in the US.
The game runs passably on my computer this way, even though everything but my video card is at or below the minimum spec printed on the box. The two biggest issues are lag when there's too much stuff on the screen (usually only happens in large groups) and that I have to relog after playing for 5 hours or so because the rendering gradually slows down to a noticable chop.
I hope this helps someone. Let's cross our fingers and hope the game still runs in Linux after the next update. :P