I have Brewed with and how many times, Wlp550 (1), Wlp500 (1), Wyeast 3787 (4), 3522 (2) Wyeast French/Belgian (Unibroue) (4)
My Favorites are for a Darker say Dubbel, Dark Strong etc has to be 3787 (Trappist) Because of its spicyness and dark stone fruit esters. For My lighter beers it is Unibroue, I like the suttle esters and fruityness it creates and how easy the beer can change with ester's due to higher/lower pitch rates and or pitching and fermentation tempratures. When I pitched it @ 26 and let it ramp to 29 the profile was of lollies and apples and pears exactly like St Bernardus 12, but when you pitch a 18 and let it raise to 22 it has a fruity subdued spicyness. I like Wlp550 and Ardness but I really like that lollie type fruityness and little spice in my Blondes, Goldens and Tripples.
I don't particular care for 3787, it's a bit too phenolic for me, but I've only used it a couple of times. I've got a blonde in a keg and 2 big ones still in secondary using 1214 or WPL500 I think is the equivalent. too early to say much about the big ones but the blonde is alright but its got sort of a lager character to it that I'm not a fan of. all pitched at 18 and ramped to 21, then finished off at 24.
I got a lot of glue off the first JP (Tripel) trial that used the Westamalle - we tried 4 different strains at a Regionals tasting. I tried it again about 7 months later at the brewery and it was really nice. I could be wrong but I'm sure Richard said it was one of their favourites after aging.
I've never used it. I'm not a big fan of Westmalle beers, though i do quite like the Tripel when it is pretty fresh. Has a really nice, and quite unique, hop aroma.