I suppose it's all been said, but...
I started using Slackware on an old 120MHz 8mb Olivetti laptop that someone gave to me. I had used SuSE a little bit but hadn't really used the command line much at all. I knew this would not install on such an old machine so looked around for something that would - Slackware seemed to fit the bill although I had to go for an older version (the current one was 7.0) - so I used 4.0. I thought that the installation was actually fairly easy although I did a lot of reading beforehand. Configuring it was really what I found difficult. In the end I managed to get everything working as it should. Took me a long time but I learnt a lot and it was fun learning.
As for whether Slackware is a good OS for newbies I think: yes as long as they want to learn about Linux and how it works. I've tried out all sorts of other stuff since - QNX, Plan 9, Debian, Red Hat, but I always come back to Slackware because I have more idea what I am doing with it because I was forced to learn so much in order to get it working that first time.