[Closed] "Go Pros".... what is the best budget alternative?

Let us know which one you went for anyway!

I have read and seen that SJ4000 doesnt have good light to dark transition (kind of essential for mountain biking).

I read that too but mine seems to have coped ok on a test run in the car (by no means a conclusive test)
Elsewhere in the review he also adjusts the settings and improves it's dark performance (shows footage inside the Printworks in Manchester), plus the more recent firmware updates have apparently addressed it as well, although I have no idea how or if it's improved
Might get an idea on Saturday when I hopefully take it for it's first play

Anyone bought a virb and used it since they popped up in this thread?

You can buy a GoPro for £100. It's the basic one, but still a pretty great bit of kit.