if you can wait a bit, I might be able to post up some really decent wedding pictures I took with the DA40mm Limited and the Pentax AF540FGZ flash. It's hard to stay away from Pentax limited lenses once you get started :P
That being said, I think the DA21 or DA70 might be better, depending on what you want. The DA40mm is more like a mid telephoto lens in my opinion. So not really full telephoto, but not a wide angle either. Pretty okay for close ups and really framing the picture'.
If you plan to do a lot of walk around and scenery pictures, take the DA21. I"m using an SMC-M 28mm F2.8 right now for that (manual focus) and the wider angle is better for walking around and landscapes than the DA40.
If you plan to do portraits and closeups, the DA70 is hard to beat
That being said, I've gained a certain photographic style by using the DA40 Limited. I absolutely love this lens.
edit: have some pictures for demo (to show you what I've done with the DA40, and also the focal length of this bad boy).
This one is with flash.