Believe it or not, but we've had very few people even willing to entertain the thought of spending the 10k or so on a Jim's 120" The majority of people doing big motors are building on what they have. They end up spending more in the long run but it seems easier to spend 5K three times vs spending 10k once. Go figure!
Anyway, we recently sold a Jims 120" in it's advertised form (no little tweaks or substitutions) and I'm waiting for him to get some break-in miles on it before we dyno it. I have no reason to believe it won't make similar power to the 120"s we've built out of customers motors. IE 120hp and 130ftlbs tq.
As far as reliability goes, I think it's a winner. The crank is the key. The two main players in stroker cranks are S&S and Jims. I prefer the Jims because they use the stock dia. TC88 strait-press pin. The S&S uses the Evo dia. tapered pin. I don't have the dimensions memorized, but the Jim's pin is around 1/4" larger dia. than the S&S one. The Jim's crank is not rebuildable like the S&S but I believe the larger dia. would hold up better and rebuilding shouldn't be required. However, let me say that I have never seen or heard of a Twin Cam S&S stroker crank failing.
Also, the Jims cases are made of a better material than stock and retain Timken bearings (a bonus for 03 and later guys).