Jono,
How old is your 1100 and how many miles has it got on it?
The answer is simply personal preference, however, here's my two pennies worth.
I know allot of GS'ers change simply because its new and that’s great if you've got a few thousand pounds burning a hole in your pocket, but whether the bikes are technically that different enough to justify the price is doubtful.
Ok you get an extra few CC, but so what, in real terms this makes little difference. I have an 1100, which in side-by-side test is faster than newer 1150's. Having ridden the 1150 on and off-road I can say that the gearbox is a little smoother, but I don’t find a problem with the 1100 anyway. The gearing ratios on the 1100 are also a little more useful than the 1150's. Talk to a few 1150 owners and most will admit to not regularly using the 1150's 6th rear (overdrive).
You'll also notice a fair few post about the poorer build quality of the 1150 compared to the 1100's. Having owned my current 1100 for 3 years and having ridden it in all weather and conditions, it's still mint, no rust, and no peeling paint. Problems with the 1150's build quality seem primarily to do with the front stanchions (forks), wheel rims and spokes; a couple of riders have mentioned peeling paint on the frame.
Lighting: Almost all 1150 riders I've spoken to complain about the headlight set-up. The 1100's light isn't great but it's certainly better than the 115o's, you've only got to look at the amount of riders on this board looking to add additional lighting to their bikes to get an idea of the problem. If you want better lighting on your 1100 get a set of twin headlights from Touratech, I've got a set and find them a big improvement over what I thought was acceptable anyway. Aesthetically I like the look of the twin light set-up compared to the big single lens.
The suspension on the 1150 is the same Showa shock set as the 1100, so if you want your bike to feel new and improved, why not treat yourself to a set of Ohlins/Hagon's/Fouranles shocks. I've got Ohlins on mine and the difference is breathtaking, it really does feel like a different/new bike. Great handing (it was good before), smooth corners and they provide feedback which makes you feel truly planted to the road, all-in-all confidence inspiring and at a fraction of the price of trading in your 1100 and shelling out for an 1150.
I don't know how stock your bike is, but consider the following if you haven’t already:
New suspension (as above)
Aftermarket silencer, straight through connecting tube (referred to as Y-piece). Releases more of the bikes power and makes the bike sound like it's looks suggest it should, without being loud enough to cause offence, Remus or Laser are good choices.
BBPower chip or Laser chip to increase mid-range bhp and smooth out power band. Also stops any surging issues, that the 1100 and 1150 have been known to suffer from.
You could go on adding forever, and this BB is great for ideas. Personally, I think you should stick with 1100. If you've made all the mods above and you just fancy a change then go get an 1150. If you haven’t, well by just changing the shocks, getting a spray job and changing the exhaust, you’ll have a new toy and one that you'll probably get on better with having been directly involved in the changes.
Hope this helps
Cheers
Simon T
