Which model of Mac hardware are you using? What sort of crashes are you experiencing (application unexpectedly quits, or system locks up, or kernel panic, etc.)?
I had some crashes when I first got my G5 when using iDVD, due to a RAM module that was not inserted properly by the retailer. Once that was fixed, the crashes stopped and it's been rock-solid since then.
Easy to learn and use, video rendering quality ok, Vegas. Counter-intutiive, complicated, difficult to learn, better rendering quality Premiere with After Effects. Both are pretty stable. If you want real-time effects, you're looking at $1500-$3500 just for the video card.