I've just started playing with Bootstrap and I'm loving it. I have a pragmatic mind and less of an artistic mind - a.k.a I have no art skills. It makes it really easy to get a nice looking interface quickly so I can test an idea and actually see what it'll look like with minimal effort.
Plus, I can focus more on the implementation of the backend code and less time worrying about making all of the stylesheets, etc.
I've actually been somewhat interested in this as well. I've only started fleshing out an idea and playing with App Engine and Amazon S3. I'm actually thinking of offering what I've been working on as a SaaS in the future but I don't know where to start.
I don't want to hijack the topic but I'll be keeping an eye out for any advice anyone has to offer.
Plus, I can focus more on the implementation of the backend code and less time worrying about making all of the stylesheets, etc.