I've got one of these and am very pleased with it. Lifetime warrenty, £250 off ebay. Rear boxes don't hang low like prospeed, fits well, good build quality and sound is nice, deep but not too loud at cruise. Mid range torque feels significantly better. Top end power feels a bit better than standard, as good as most s/s exhausts unless you rid the cat I expect.
Blueflame has no middlebox and decent size bore (63mm) so less restrictive than standard, and no 'tick tick tick' when you pull up, like the standard exhaust does on cooling. PM me if you want accel /driveby videos.