The fps display in the editor is actually linked to the refresh rate of your monitor so you might get an upper limit of 60, 75 etc depending on your monitor setup. This is deliberate I think but I can't remember why, I think it's to display an actual frame rate rather than a threoretical one.

I would say that GameCore is stable and capable of releasing a finished game. The developers have recently finished one but it's not available yet. I think it's a casual tie-in game for a childrens TV show. I haven't personally, but I'm getting further with GameCore than any other engine, including 3DGS. It's now my engine of choice, it's dead simple workflow seems to suit me very well. I do struggle a bit because I'm an amateur programmer and tutorials are scarce.

Speedwise I'd have to say it's fine, I've certainly had no problems even with loads of polygons on screen. The physics engine is capable of handling literally hundreds of objects. The demo's are just templates designed to be easily accessible, they're not really there to show off. Rachet is right though, we haven't actually seen a fullblown game running to see how well it does so there's no real proof.

BV had some major issues, I feel this overshadowed an otherwise great product. The biggest problem so far has been a lack of support rather than a bad tool. At this point there is still a question mark over support, i.e. if you discover a bug today, there's no guarentee it will be fixed in a reasonable timeframe so you could be left waiting. However this has dramatically improved in the last few weeks under the new owners, they're evidently investing in it, hiring a lot of new staff and I'm pretty confident things are going to get even better. I don't want to sing it's praises too much, I'm starting to sound like a GameCore salesman