I made a pumpkin beer last year going off of Jamil's recipe and adding ~3.5 lbs of canned pumpkin to the mash. I added about half a pound of rice hulls and didn't have any problems with lautering. That beer came out AWESOME! Multiple people at our Halloween party said that it was the best pumpkin beer they had ever had. I am brewing it again on Labor Day.
In all honesty, the pumpkin doesn't add much, if any, fermentables. The spices are what make it taste like pumpkin beer. If you don't want to risk stuck sparges or deal with the mess that pumpkin adds to the fermenter, just skip it.
Not everyone likes pumpkin beers (as a few posters mention), but I love them in the fall. If you like pumpkin beers, I highly recommend brewing one. If you're not sure about a recipe to use, Jamil's from BCS, is excellent.