Try emulating any of the "Need For Speed" games, which made tonnes of use of graphics tricks.
That said I do appreciate their efforts, it's just we're still a way off until it could be considered complete.
Timing remains my main problem with emulation. Input and output lag have gotten really bad and so hard to predict until you start actually messing with the equipment you'll be using, and even then little config quirks or the way things are hooked up (adding a receiver to the mix, for instance) can throw it all over the place. Lots of games become unplayable or unreasonably hard with just a little extra lag, so it's a real problem.
For most games, VU borrowing "cycles" from CPU can help a great deal, so can enabling the threading. The defaults are the most compatible, but also slowest.
Also, GSDX is the only gpu plugin that works semi-decently, and only with actual DirectX. Opengl is all over the place.
Most games work fine even on a ten year old computer, with these settings, as long as you're on Windows.
Linux support could be better, but there's no manpower for that. It is kept alive by one or two developers who use Linux, most of the team being on Windows.