I think the 850F are a huge jump from the 825Pro's - certainly not an evolution. I swung both at fitting (along with a bunch of other clubs) and it was night and day. A shame really as now the 825Pro's can be had for a good price and if they had been close, I would consider them for an extra (other location) set.
Aww, don't say that. I was fitted into my 825 Pros based mainly on their feel and consistency and was thinking that I'd let the 850s just sort of go by figuring they would be in the same ballpark performancewise. Now I feel like I need to try the 850s because they're that much better...