Thansk for the resposnes guys. How long do you find you get our of your batteries? Are they only ~50% drain types, so you get around 5 hours use? I'm trying to do it a bit cheaper since the mount is already blowing my budget - puts $240 at too high a price to pay. I figure I'd only be using maybe 3-4 hours of juice since I don't see myself sitting out in the cold all night and it should be enough to get some good shots. Of course there is the AP-bug where I'm sure I'll have to upgrade and buy all sorts of accessories later, but we'll deal with that when the time comes
One of the reasons I was looking at the lithium batteries was the charging.. they come with a wall charger and I don't have to deal with hydrogen peroxide gas being created with some of the lead batteries. I also like that about the jump start pack, but I've read that some battery types are better for this sort of use than others. Another reason is the weight. Most of the 12V batteries I've seen (car, marine etc) tend to be pretty hefty and it would be nice to retain some decorum of portability with my rig. At the moment it's mount (~10kg?) + camera + lens, so it's manageable.
Cheers.