Yeah, the Montreal Maple Leaf Lounge is quite nice! I had pretty much the same reaction as LPCJr when visiting it for the first time. It's not huge but has a very spacious feel, has a nice view of the airport, and is a comfortable place to relax before a flight. But the main difference, for those of us used to US Clubs, is the quality of the victuals -- good drinks and good food, all complimentary. Last time I was there they had a very decent salad among other snacks.
I guess that's a good thing about the US Clubs: they don't spoil you. Spend enough time in the aging furniture at B/C in PHL, and a visit to the Maple Leaf Lounge becomes an exciting and wondrous change of pace.
The only amenity the MLL doesn't have that I would have liked is complimentary wireless internet. It does have wireless, but it's not free. (Just like US clubs.)
The Envoy lounge is the best comparison at US, since it has free drinks and some food. This lounge is available to Envoy class and *G passengers on international flights through PHL. (This is still true, right?? it's been many months since I travelled Envoy...)