To start you off - here's an image of said bike. Personally I really like it, it's tasteful and actually discreet amongst all the garish yellow and near-neon blue bikes parked everywhere.
Talking you through some of the mods, the bike has a TTX36 rear shock, NIX30 cartridges, Brembo RCS19 + Brembo M4 calipers running EBC GPFAX pads and the bike produced a staggering 194bhp at the wheel - there's also a Translogic quickshifter to make the most of all of that goodness! there's a feast of aftermarket ergonomic parts such as the taller comfort seat for the owner who is over 6ft tall.
Sitting on the stationary BMW it feels bigger than my ZX6R, probably down to the larger seat but also in terms of reach to the bars. I found the steering to be very heavy when stationary but the moment you start moving it becomes VERY light but fluid - I'm not used to this with my ZX6R.
Exit pit lane, half throttle is quick, popping 2nd gear throughto 3rd and it pops on the quickshifter. Tip it into turn one and I feel like I'm gliding - the owner is significantly heavier than myself and I was expecting the bike to feel very harsh but this was not the case. Turns 1-3 can be taken as one long turn and it feels sublime on this thing. Down to 1st for turn 3 then short shift for the left hander turn 4 onto the back straight - I'm only rolling on and using half the revs shifting through to 4th and it feels like it gains torque in every gear. This thing is a rocket.
Now - I went out in Novice group for this session (I had been riding in fast group myself) so I did promise Claire at NoLimits that I wouldn't go mental and I stayed true to my word.
A couple of laps in I started to press on the brakes more and I wasn't impressed. A LOT of lever pressure was required and all of a sudden the bike felt very heavy. IMO, the brake pads were the weak point in the system - they felt exactly the same as the EBC HH I tried before. Also, his brake discs were warped badly and I later found out they're original... 6000 miles (5000 miles on circuit).
Half way through the session the track become nearly empty and I saw the opportunity to increase the pace - I was lapping around 2m20 and decided to do some 2m08 laps (10 seconds slower than fast group). The POWER

The confidence I had in that bike to get me through every corner and ping me out the other side was phenomenal - it really was. It's partly the reason I bought myself some Ohlins...

So how did it leave me feeling? Do I want to trade in my 600 for a 1000? Mmm... No. No I don't because I didn't enjoy it as much as I enjoy ragging every inch of life out of my 600. The bike is phenomenal and far superior to mine and I guess that maybe I like to be at one with the bike, this bike was better than me.
Would I go faster on a 1000? I'm certain I would. If this BMW was my bike I would easily have gone 3-5 seconds faster than on my ZX6R and I'd have been doing 1m53s.
Am I glad I rode it? Oh yes.. I really appreciated the opportunity and I'm very happy to say I did it !!