I'm embarrassed to admit that I've been gleaning valuable information from this site for a number of years, but haven't posted until now.
I'm in the middle of doing some side-by-side yeast comparisons, and I'm interested in how Lallemand Abbaye compares to the more established Belgian strains. I recently bottled an all-grain BIAB batch of the Belgian Dubbel from Brewing Classic Styles (which I highly recommend if you don't have it), which I split between Lallemand Abbaye and WLP500 (supposed "Chimay" yeast). I brew small batches (about 1.5 gal at a time), so I split it into 2 1-gallon jugs (no oxygenation or yeast nutrient), and let ferment in my basement at about 65-67 ambient. With such low thermal mass in each fermentor, there wasn't any noticeable temperature increase from fermentation.
I rehydrated 1 tsp of Abbaye (probably about 4 grams) and pitched this along with 1/2 vial of WLP500 (not 100% sanitary, but it's how I stretch my yeast dollars with such small batches). Interestingly, the Abbaye started and finished fermentation about 24 hours before the White Labs. Carbonated everything to about 3.0 vol CO2.
Both batches have been in the bottle only 2 weeks as of today, but I opened one of each this weekend, and they taste remarkably similar. I would say the fruity esters are a little stronger with WLP500, and Abbaye has just a little more spiciness too it (kind of a cross between WLP500 and WLP530). If I had to choose a winner right how, I'd say I like Abbaye better, but I'll have to let the bottles age a few months before I can really evaluate them.
I plan to brew the basic Belgian Blonde Ale (like Leffe) from Brewing Classic Styles soon with the same yeasts and fermentation conditions, so I can compare light vs dark Belgian styles with these yeasts. I'll report back when that's done.
But so far, I'm pleasantly surprised with Lallemand Abbaye and would recommend it.