major difference between 20 and 30 is the hv30 has 30p. Theres a ton of threads and sites about it, search ns/google. Theres also a hv40 which has improved 24p, but i wouldnt spend the extra $$ unless your a searous filmmaker, and i dont feel like you are
Acessories i have:
Bower fish eye lens
http://www.amazon.com/gp/product/B000HAQ8XG
Cheap Lens Hood
http://www.amazon.com/gp/product/B0019BGDPA
Filter Pack
http://www.amazon.com/gp/product/B001KN6WL2
UV filter does basicly nothing but keeps snow out of the lens cap mechanism
Polarizer is good at reducing light on blue bird days to open the aparature
Havnt used the Floresent
Manual Focus Ring
http://www.irvdesign.com/product/mfr/
Lets you manual focus like on a pro camera
I bought a DM-50 microphone, it hasnt shipped yet
http://www.amazon.com/gp/product/B00005LD4W/
Couple more tips:
Get a couple batteries, they dont work as long in cold conditions
Get a good hard case for holding your stuff and a good back pack for skiing with it.
Try to find a small but sturdy tripod you can take on the mountian with you
The HV30 doesnt come with a firewire cable(wtf), buy one at the same time
Check out
hv20.com