I have done a lot of soul-searching because I was having problems with WordPress just recently after using it fairly happily (and recommending it enthusiastically) for the past 8 or 9 months. To be fair, the problem turned out to be a third-party plugin. But now I'm trying to combat spam onslaughts while still keeping my comments open to readers (right now, the comments don't work; I don' t know why).
I came from MT to WordPress last March. It took some getting used to and of course people want to feel comfortable so they immediately start comparing the new tool with the one they had (kind of like you do with a new beau!). Anyway, I really like a lot of things it can do, so when I had these big problems this past weekend, I was out there downloading and investigating new blog tools (kinda like a newly divorced woman trolling the bars looking for a new mate!). None held a candle to WordPress, although they EACH had features that I wished WordPress had. That was not enough to sway me from my desire to use WordPress if possible. Why? Because there are just certain things I want my blog to do and the others just don't do them. Not well enough to suit me anyway. So I returned to WordPress, rolled up my sleeve and fortunately found and solved my big problem. Now I just have a few little problems.
My point to this rambling post is that you have to decide for yourself what you want. Just as with people, you probably won't find anything that fulfills your every need. You just have to find something that has MOST of the features you want, or at least the most important ones. If you are going to be blogging, you are going to be interacting with your blogging software quite a bit. It should not be or become a chore. If it does, then it is indeed time to go shopping around again.
While I'm not minimizing the items on your wishlist, in the big scheme of blogtools, those shouldn't be deal breakers. You can create a theme or skin of your heart's desire if you want to, as most blog tools have an administrative stylesheet that if you are clever enough to do so, you can change as much or as little as you want or need.
You don't mention the plugins that are important to you, but I've been out there and looked at Pivot, TextPattern (I use it on my web design site, but am not really considering it for my blog), B2 Evolution and yes, even MT 3.1. No other blog tool implements Amazon in the way that WordPress does. Call me spoiled, but I just love it.
Now if I can get the comments issue sewn up I'll be a truly happy camper.
I hope you find the tool that suits your needs. If you want certain plugins, you may want to stick to the more popular tools out there (MT, WordPress, etc.) since they have the largest user base and it's usually those capable users who come up with the innovative plugins. A smaller, lesser known blog tool won't have that user base to draw its knowledge from.
Go here: http://www.opensourcecms.com -- you can try demo versions of just about everything out there. Surely there's something out there just for you! If not, as someone else suggested, write your own! A lot of people do!