A quick Google search indicates that plenty of people are running DVD copying tools with no problems on Vista RCs.
There is vastly more to Vista than a massive GUI overhaul. The differences can be subtle to an experienced user but a vast array of things that confused people and lead to tech support calls have been improved. Also, a massive number of things that needed post hoc adjustment on XP installations are now standard.
The really big stuff is under the hood. Developers who've gotten a taste of the new infrastructure are very much looking forward to the day when they can write exclusively for Vista and what comes after. Much like the early Win95 era, it will take a good while before the difference can really be appreciated in packages beyond Office. (Even the first 32-bit rev of Office was lacking and didn't really make full use of the Win32 environment until Office 97.)
Since it's only going to be a few months before most new PCs ship with Vista, I have little choice but to get well acquainted with it so I can perform my freelance IT work. I have little interest in high-end PC gaming, so assembling a capable system won't cost much. I recently picked up a 256MB Nvidia 6200 AGP card for $25 AR. Someone more desparate for DX9 support can get an ATI 9950 128MB card from Fry's right now for $10 AR.
Beyond that, just make sure you have at least a gig of RAM and the slots to easily add more.
The 15% slowdown in games is something of a misnomer. That estimate was for Vista running on the same hardware as an existing XP system. But the majority of Vista systems will be new machines with far better specs than the average existing XP box. By the time Vista is hitting high market penetration an $800 system is going to have a quad-core CPU and other niceties that are not even on the market yet. The collective advantages of the new hardware combined with Vista will make that speed difference on old machines a passing memory.
People have forgotten that XP could be quite impaired running on a machine that was considered high-end for Win9x. But how many serious gamers would be running such dated hardware by the time XP launched?