Jess,
Of the three products you mentioned, Mere Mortals is the only one that is an application framework. The others are component collections, which are very handy, but it doesn't sound like that's what you're looking for.

I use Developers Express for components, because for masked edit boxes in particular they have more of the feel that my Foxpro users are familiar with. (i.e., pressing tab brings you to the next control, not the next section of the phone # in the same control). I recommend it, and have been very happy with their support and documentation.

I printed out Mere Mortals' documentation, which is available on their web, and plan to get it. After some small applications, I see more and more the need for a true application framework like I was used to in Foxpro. Take a look at their documentation and see what you think. I haven't seen any other application framework, just component collections and data access class libraries/generators.

Good luck.