Thanks to everyone who commented in my last diary. Your comments were extremely helpful, and definitely changed my mind about what I should be looking for.

It turns out that the store mentioned in the previous diary has a surprisingly detailed website. With this in mind, we enter round 2: Which specific bike do you recommend?

1. It seems clear that I want either a mountain bike with slicks or a cyclo-cross.
2. I think 256 is being very wise when he suggests losing the straight bars. The only bike trip I've done in something like 8 years was last year. It was only 100km or so, but it was on a mountain bike and my wrists (and, to be fair, ass and legs) were on fire by the end of it.
3. I really, really need a way to carry stuff. Ad hoc paints a grim picture of carrying large amounts of stuff on your back, and gives several helpful suggestions for alternatives. It seems that while I could work around a lack of attachment points on the frame, the more built in carrying capacity I have the better.
4. I'm 6'1"ish. The website mentions when they only have the bike in miniscual sizes, so those can be safely ruled out.

I'm still feeling pretty fucking overwhelmed with options here. I'll take any advice offered here pretty seriously, so if anyone wants to spend a few seconds window shopping and helpfully pointing out any particularly alluring options, I'd be most grateful.