I've had the HERO 1, 2 and currently have the 3.
-The 1 is garbage. Terrible quality and audio.
-The 2 has much better video quality but is pretty bulky and heavy. It ended up facing upside down while mounted to my helmet very often while snowboarding.
-And I'd say the 3 is really their first camera you can actually tell is HD.
I'd say the 2 is the best option since you're just gong to be using it casually. Since I use mine weekly except for between October and skiing season, I always upgrade to the newest model when I can.
Uses: Stock car racing, snowboarding and waterskiing