I have made two pumpkin ales, one last year and one just last night in fact. I boiled the pumpkin purée in a heavy duty mesh bag used for wine making I think. I had great pumpkin flavor. Last years recipe may have been thunderstrucks but not sure.
Also I listened to a podcast from the beer smith website. One of the guests mentioned to boil the purée as opposed to mashing it. I'll try to find it and post.
Punkilweizen sounds like it would be awesome. BTW Costco has organic pumpkin purée for $8.00. There are six 15oz cans. I used all of them. Can't wait to try this years pumpkin ale.
Good luck man.