I use XMAME/XMESS 0.37b10.1 with the Glide Renderer. I have a Glide patch and kernel module that programs the Chrontel 7001 video encoder thus enabling S-VIDEO and composite output and disables bilinear filtering in the Glide renderer. I use an Obsidian X-24 which is essentially two V2's sandwiched on a single card and has _excellent_ TV output (much better IMHO, than the V3's). Similar boards are used in arcade hardware, and these can be had for cheap nowawadys on E-bay (I think I pad ~$75 new about a year ago, IIRC, they cost ~$800 when new!). The module _should_ work with the Canopus cards since they use the same Chrontel chip, but I think the i2c buses are slightly different on the cards.
Now, before you laugh at the idea of using a V2, remember - we're not using the 3D stuff (well, _technically_ we are). The advantage to using the Glide renderer is that you don't need X - *at all* to run MAME/MESS. You can run the emulator directory from the commandline which is wonderful for an ersatz "embedded" type of application (more room for ROMS on your CD). Oh, and did I mention it's nearly twice as fast as the OpenGL renderer
Using a BP6 with two Cel 366's @ 550 (but you really don't need SMP) for this setup, all but the very newest of games run at seemingly native speed. The Glide renderer is quite amazing. The NEO GEO emulation is absolutely perfect.
What I'm working on now is an ISO that is a complete bootable Linux distro on CD. The idea is that you don't need to know jack about Linux, just boot the CD and you're off using your multi-emulator menu driven setup. Ideally, I'd like to make an optional patch for Daphne that (sorry Matt!) removes the dependance on a GUI so that we don't need to incorporate X into the distro. As far as I can see, the only need for graphics in the Linux version is the scoreboard. What I'd like to do is make a "generic" scoreboard for the cabinet project that can work with various games (but this is something down the road).
EDIT: I failed Inglish class.