Got the BT45's fitted yesterday along with my 12k mile service.
Cost was �65 front and �70 rear plus fitting.
First impressions are pretty reasonable. Small but not massive difference in noise or smoothness to the siracs. The main thing that did suprise me is that they handle cat-eyes and poor road surfaces and overbanding much better than the siracs. The siracs seemed get really unstale if there was anything at an angle it could grip (edge of a speed hump, overbanding, cat-eye, camber/troughs in the road) wheras the BT45 seems quite at home in those conditions. Might not sound like much but it give much more confidence when filtering between lanes on the motorway. I used to be have to be very wary of the overbanding and cat-eyes on the siracs as i got kicked sideways by the tyres, now i'm just aware i've gone over a bump
Also took some more back roads home from the dealers and feel much more confident on roads with lots of patchwork roadworks and cambers that can't make their mind up which way their going.
Hard to comment much more that that as the siracs were fairly square and I was a very new rider when they were still round. It still feels like the BT45's give more confidence than I had before and seem to turn in a little bit more readily.
Should help with my confidence levels as I try to improve my road riding with the IAM. Once these are worn I might try the tourances a go and then the siracs again afterwards to give me a good idea of what each one is like before settling on one type. If the others last as long as the siracs do however it'll be 2010 before I've tried them all!