Come on, let's get real! The 1100 is a great bike. I loved mine for 4 years and 60,000 miles. And I've recently refreshed my memory by renting one. The 1150 is SUBSTANTIALLY better in some very important respects.
- the gear change: the 1150's feels like a modern bike, the 1100's feels like a tractor
- the extra gear ratio - high speeds on motorways on the 1100 are much harder work, tons of vibes, not nice at all.
- the smoother, gruntier motor thanks to the much better valve gear 'n stuff that first appeared on the R1100S
- reliability. Early 1100s were dreadful - mine was always on the back of an RAC truck - but the 1150 has been remarkably bug free.
- the exhaust note - the 1100 sounds like a broken strimmer. The 1150 sounds like a motorbike
The 1150 was a backward step in only one respect - the bars are stupidly wide. A real pain in London traffic. I had mine cut down.
Oh. and plastic tanks on early 1100s feel lovely, look lovely and have an amazing useable capacity.
I rest my case!