I am a big fan of nucleus ( which is what is used as the backend script for this site ).
Why ?
The first choice to be made when anyone looks for a weblog script is to decide whether to go for static publishing or dynamic publishing. Dynamic publishing can be a big overhead if you have a lot of visitors and the database chokes on the number of connections per second. On the other hand, static publishing can be a big pain if you change your templates or skins as frequently as I do.
I did play around with movable type for some time but found it incredibly slow. Again, the fact that 2.51 might be the last free version ( ? ) put me off. I didnt want to get stuck with something which will not move forward unless I pay for it.
I found nucleus to be a well-designed script with a really cool plugin interface which enables me to extend the script in whatever direction that I want without bothering karma :-)
I have been writing a few plugins for nucleus like the Macros plugin or the Ping pong plugin or a few others about which you can find more information here.
Today, I have coded up something which I wanted for a really long time. Click on the comments link and check out my new threaded comments plugin. This is alpha code. So please be gentle with it. If you come across any errors, kindly send me a mail with a small explanation of what went wrong.
Enjoy :-)