I have read that a lot of editing software will not let you edit 24p footage, which you will probably want to do since it's the HV20's party piece. Only Sony Vegas software (AFAIK) works well with 24p (and all the other xxp's too) and in my opinion is the best editing sofware out there for PC.
Steer well clear of all Pinnacle software as its generally buggy. I have not used anything of theirs since Studio 8, but that was a nightmare. I hear studio 11 is also very buggy.
Go for Vegas 8. If you're feeling flush Vegas Pro 8 is great, but don't expect a cuddly 'fisher price' interface like in Pinnacle.
I've never used Adobe stuff so I can't comment on it. I don't think it will upload and edit 24p. Maybe someine in the know might confirm that?