Ballistics Report
Workmanship: 
Yamaha has a strong background in audio, and it shows in the design of their flagship sound card. Initial newsgroup reports indicate that the digital SP/DIF output may be the best of any currently available sound card, and that the line-in is exceptionally quiet. However, be careful, as the Waveforce Digital has cleaner sound than the regular Waveforce, due to the presence of the on-board amplifier for amplified speaker out. You're also getting something intangible with the Waveforce-the Yamaha reputation. It's a Yamaha chipset on a Yamaha designed card, not some cookie-cutter clone of a third party chipset, and these guys invented the XG MIDI standard!
Technology: 
While the EAX reverb effects were solid, I didn't find the 3D positioning quite as compelling in real gameplay. That, combined with the high CPU usage figures for 3D sound, indicate that this is certainly not a card for 3D sound mavens. The bottom line, as always, is in the real world gaming results, and the card does a good job of keeping framerates high in EAX games. Although the 3D sound may not be as sophisticated as the MX300, it's still worlds better than basic stereo.
Software: 
I found the driver to be simple and straightforward, unlike the gadget-laden install of the SoundBlaster Live, and it worked the first time. It was thoughtful of Yamaha to make the optional components a separate install rather than loading up my system with a bunch of stuff I may not want.
The legacy DOS support works well with the few DOS games I had left to test with. This sound card also happens to be one of the few PCI sound cards supported in any form on the Linux platform, if that's your bag.
I was a little disappointed that the MIDI functions were performed by a software synthesizer. After all, why buy a Yamaha sound card if I can install the high end XG MIDI on any PCI sound card and get the same exact sound? The bundled software was also very MIDI heavy. If MIDI is your thing, especially XG MIDI, you'll have a blast with the included software. However, the game bundle is forgettable, consisting of lite versions of games you probably completed a year ago.
Compatibility: 
It should go without saying that any MIDI file you can find will sound great on this card-that is, with the appropriate software synthesizer installed.
The Waveforce sports excellent EAX compatibility, thanks to Sensaura's 3D technology, and is a huge benefit to gamers. EAX is an open standard based on DirectSound3D, and we're seeing more and more titles with either DirectSound3D or EAX support. Either way, you'll be getting the most out of your sound card in games for the foreseeable future.
A3D support is questionable at best. Only older A3D 1.0 titles will work with this card, and it's definitely something that Aureal is trying their best to stamp out. It's not a great loss, since you've always got EAX to fall back on, and EAX is layered on DirectSound 3D, so you will still get 3D sound even if you don't have A3D support.
Price: 
The street prices for the Waveforce are about $100 for the digital model with the SP/DIF output, and $60 for the standard model with amplified speaker out. This is certainly competitive with other sound card offerings on the market, and I think it's reasonable for what you get. The only serious omission is four speaker support.