I spent 3 years developing modules in Rainbow and really liked it. Too bad it just faded away and went stagnant about 4 years ago. I see some similarities between Rainbow and mojoPortal which explains to me that Joe did use and liked Rainbow.
After Rainbow I spent 6 months in DNN and it was ok for development but... DNN is so slow performance wise you need a good server to pump out that code which people sometimes don't find with shared hosting. Man..... is DNN slow.
Finding MojoPortal a month ago has been huge for me. It's the first time I've been excited about developing in nany years. mojoPortal is just TOO GOOD!!!
I am building 2 modules right now. One for a non-profit club I belong to and one for my employer. I am using Telerik controls inside the modules and they work fine. Their Radgrid is very flexable. For DAL and CRUD I am using Teleriks OpenAccess ORM tool. I am new to it but It's very good. They even have a free Express Edition of it. here It's worth a look.
Calgary, Alberta , Canada