I have probably said it before but will say again … WordPress is great. I spend most of my day writing and reviewing code at work and is nice to be able to write in words for a change.
Word press is built with PHP – I know PHP has it's critics and sure there is a lot of hacked together PHP scripts out there but I am sure there are is a lot of good code also. WordPress is it's real success story (sorry not a facebooker) in my opinion.
In the past I have dug into the code base and found it a little hairy (used to OOP) – this was years ago though. I don't know what it looks like now, and whatever about the code base the ui seems to be orgainzed very well.
WordPress is just so flexible and straight forward and is great fun. Not sure about using it for businesses to be honest – have been there before and I think eventually you out grow it. Small businesses should be fine!