When I started to play with the SDK, using scratchbox 1, I was very disappointed with the way it works. It is just too much different from how I personally prefer to work. I was even surprised to find out there are people more familiar with working that way than just using a cross-compiler in a "normal" environment. And I go as far as to blame the quirkiness of the classical SDK for slowing down the speed maemo could be evolving!... I don't say there should be only one way to develop, but SDK+ took/is taking too long to appear.

Lucky me, SDK+ based on scratchbox 2 is arriving... But to me using it is more of a vanity thing. In your case I would recommend, as Nathan did, the most vanilla installation possible, so go with scratchbox 1, unless you have a very hard time with it, like I did, and decide to face the consequences of moving to the "experimental" alternative. Regarding Qt, I don't have experience with it, but afaik the existing packages are pretty much reliable.