Hi Chris:
My take on fleece is that it's best for put on and never take off conditions, which for me usually means below freezing. If I were hiking, backpacking, or cross country skiing above those temperatures and were wearing a shell and a base layer, I wouldn't go any thicker than a Patagonia R1. And if I needed something warm for stops, I'd throw on a down jacket or a synthetic parka like the Patagonia DAS.
Having said that, I wear fleece all the time for lift-served skiing or sitting around car camping. Here's a pic of me sitting around in an R2 at 26F:
On top I'm wearing a Patagonia R.5 shirt, then a Patagonia button down shirt made of R1 material, an R2 jacket, and a Patagonia baffled Down Parka.
This photo with me wearing a Monkeyman fleece was taken at the same place, but the temperature was 12F:
This time I have on an Icebreaker 175 base layer, a Patagonia button down shirt of about 100 weight fleece, a Monkeyman jacket, and an older Feathered Friends Rock and Ice Parka. The pants are baffled TNF Himalyans.
Obviously, I'm not suffering in either case, and could sit out all day at those temperatures wearing those clothes.
I'd say that the Monkeyman is twice as thick as the R2, and for active wear is too warm for anything above freezing. But it certainly is luxurious, and not without a certain tactile appeal to those of the opposite sex.
As for the R2, I think it's the best incarnation of fleece yet made, and I wish that Patagonia made pants out of the material.
Also, the Monkeyman is a trimmer fit than the R2 of the same marked size.
And here's a note on the R3: at one time the Patagonia R3 was made of a Malden Mills high loft fleece that was heavier than the R2 but not as think as the Monkeyman. However, the current version of R3 is of windzone fleece that is densely-woven, quite wind resistant, and doesn't have the warmth to weight ratio of either the R2 or the Monkeyman.