Hi,
I'm not really Beca, but I'm her DH, and I've been running Vista (beta and release) for a while at work. The key to getting Aero to work is having solid driver support. Make sure you have the most current drivers for your hardware - with the Vista release yesterday, many vendors will probably be posting frequent updates, so you might want to check on a pretty regular basis until your system is performing the way you want it to.
As far as enabling Aero, there is no 'turn on' or 'turn off' that I know of. Instead, the OS looks to see if the Video card/driver combination can support it. If so, it turns on. If not, it is disabled.
The way you can 'force' the OS to check again for Aero compatibility is by updating the Windows Experience Index. There are a couple of ways to get there, but I usually use System properties (either from the control panel, or by right clicking Computer in the start menu and choosing properties.)
The Windows Experience Index shows up as a number in a blue box. If you click the label, it's a hyperlink which takes you to 'Control Panel/Performance Information and Tools.' From there, you can click "Update my score" which will run the tests again and validate the system for Aero compatibility. If it doesn't work from there, then barring a driver update, I don't know of another way to turn it on.
I hope this helps,
Russ