It's significantly harder than OF I think.Monopoly (E7) at Millstone is probably the closest match for style that I can think of right now. BTI has a harder crux, is steeper, more sustained and equally bold. I'd also say it's harder than other E7 onsights I've done, but as these are few and far between it is hard to draw direct comparisons.Does this make it E8? I dunno, but I wouldn't argue.
A not too clear video of The Lovely Charlotte, gives you some idea what its like.
I've never tried S-Groove, but BTI is several orders of difficulty harder than Perimeter Walk. PW is just one not particularly hard move, BTI is several harder moves in a row and is much more tenuous.
I've rebolted Whose line is it Anyway at the Chee Cornice....
Any particular requests Neil? I've been badgering the troops to do That Was the River, which has especially shocking bolts.