Need Advice: What Software or Service for My Blog? What Should I use?

So hey, as you might've seen from my shameless text ad, I've recently started a blog, BareNaked Pundits.  Mostly, it's just for fun, but I would like to have the ability to expand it, include other authors, functionality, etc.

And that's where I need advice -- what would people recommend using?   Right now, I'm using Blogger. I like it because it's fairly easy to use, and low hassle.  But there's a few other things I'd like to have that it doesn't provide:

1. Treed comment structure, as opposed to a long list (a la DK).  

2. Ability to have user diaries (again, a la DK)

3. More choice with templates (or at least easy ability to change the look and feel.

4. Most important, easy to maintain, from a tech standpoint.  I'd really like to avoid something that requires me getting into the code on a regular basis.  I'm not code-a-phobic, but I don't want to spend my time there.

FYI, cost is not a big constraint, within reason.  I'd rather pay $20, $30, $50 a month or more for something that is functional and slick than get a half assed one for free.

I've started poking around Soapblox, which the folks at OpenLeft seem to use, and that looks kinda cool.

Basically, in a nuthshell, I'm looking for at least some of the functionality of our beloved DK, to enable better discussion, but certainly not of that scale, of course.

I'm sure there are hundreds if not thousands of folks here who've gone through a similar search, so any advice would be much appreciated.