Man, Contego is one of the few that got away, would have loved an M4 Contego. I do have it's smaller brother, the Rift, and it's one of my favorites, shame they discontinued 'em.
Haven't had it open in my pocket, and I do carry it in a way that would allow for that to happen. But I do agree it's a weak detent. I don't know why they decided to make the detents weaker, it's not just the GB2, the PM2 and Millie 2 detents are pretty weak too in recent years. My near-decade old PM2 takes about twice as much force to overcome the detent as my year-old Maxamet PM2, I've since handled other US Spydercos and the detent is consistently weak. I heard they made the detent stronger on recent GB2s but I haven't handled any other versions than my own, which I got a month after they came out.
This thread made me dig through my boxes to find my 940, gotta say I missed this knife, but I also remembered one major turn-off and probably the reason it's been sitting in its box for the past 3-4 years. It's pretty chunky behind the edge, and due to the narrow blade it gets even chunkier with each sharpening. I remember cutting apples at the office a few years back, it wasn't really cutting them, once it got past the skin it was just splitting, even my XM-18 was slicing though rather than splitting. Wasn't too happy with it. The fit and finish is awful too, there's screws poking out of the liners not sure if they fixed that on later versions, but it's pretty annoying to see on a knife in this price bracket, and a magnet for pocket lint. Out of the 4 knifeworks exclusive 940s I ordered I had to return 3, because of mangled edges and one had the worst action I've seen in my time collecting Benchmades. Even the one I kept has a fairly uneven edge, and a very visible recurve. If you do decide to go with the 940 keep in mind they rely on their customers for quality control.