If there's something I've learned from work, it's to start small. At the beginning, use pieces that are available to you already. Build quick prototypes, and only work on the hard parts as you really need them.
I've spend a considerable amount of time working on blog systems, but in the exactly opposite manner. I worry a lot about what system to use (I've switched between MT, Textpattern, and Wordpress) and through each iteration, I don't even come close to using the full feature set. Also through each iteration, I constantly neglect to keep the blog engine up-to-date with respect to upstream releases and security fixes.
I've mostly given up on tagging and categorizing, because after staring at my analytics stats for a while, I realize that the vast majority of my organic traffic is from searches. I'm sure google can index my site much better than my tags can, or MT's search engine for that matter. If people really want to know all of what I say, they should just subscribe to the feed, but as there aren't too many subscribers as far as I can tell, there's no point optimizing for that as well.
So my new consideration is to minimize the effort needed for this blog as much as possible, by moving to a system that is mostly hands free. If I move to blogger, then I get a pretty good blog engine, enough customizability for me to add adsense and analytics (the only things I usually add anyways), and I don't have to worry about upgrades. Besides, if FSJ can succeed using blogspot, then there's no reason I should have to worry about anything more complex right?
Let's just hope there's a MT4 to blogger script...