Sat both the SharePoint 2007 and WSS 3.0 Application Development beta exams today.
I found the SharePoint exam really hard, doubtful I passed that one. I'm pretty confident on the workflow and infopath questions as I've spent a fair bit of time in those areas. Also my knowledge of customizing search came in handy, but didn't really know enough about programming against the BDC and Excel Services. It highlighted a few areas that I need to look further into in the SDK.
I found the WSS 3.0 exam a bit easier. I've done a lot of development on WSS 2.0 so that knowledge came in handy. Also I have been reading the following book on developing in WSS 3.0 by Todd Bleeker which is excellent. Definitely worth the purchase price.
Still not sure I passed though as there were quite a few tricky questions in there.
If I didn't pass I will definitely be resitting these after a bit of study. It's really great that this time around Microsoft has included exams that require really deep development knowledge, as well as the IT pro exams. Basically the whole exam is focused on the object model and web services, which really reinforces firstly how much skill is required to properly program against these products, but also the potential i.e. WSS 3.0 and SharePoint are platforms for development not just out of the box products (although what you get out of the box is pretty damn good )
If your thinking of also sitting the exams this site has a pretty good list of most of the items on the exams, although not doubt official books will be released later in the year.