Our problem is the extra weight and the available time for editing. We posted on the OAT web site, a thread about editing en route. We got a lot of suggestions, but primarily everyone who did reply and who edited en route, pretty much told us that their editing was limited to backing up and deleting. No time available for anything else, which was pretty much our experience. Obviously, it's a lot lighter to carry CF cards than any kind of tablet or computer, and weight IS a factor on many OAT trips( they DO limit you ). So we opted to continue to do our editing when we returned home.
That was then. Now, we have just learned that Apple has made our three year old laptop obsolete, as that hardware cannot download their latest OS system, Lion. Apple does that, and it's the only thing we hate about that company. They actually MAKE their own products obsolete, forcing you to purchase a new one. Given that, I'll likely purchase a MacBook Air, which doesn't weigh that much and take it with me.
Respecting HDRI we're still reading up on it, and will likely purchase a program when we start to do it seriously. Given that, we'll install it on whatever we purchase and take it with us, minimizing the need to carry loads of storage, as we'll be shooting in RAW at that time.