Good thread.

Let's see now...last six bikes:
R1100S BCR (current)
HD Streetrod
HD Dyna Sport
Sprint RS
TT600
R1100R
I'd find it somewhat difficult to put into some kind of order of 'best' perhaps because they're all very different to eachother. The 2 Harleys were, surprisingly, poles apart for example.
1. For all-out 'just for fun' I'd dare say the Dyna Sport ranks very highly. Sure, it wasn't fast by any means and in a straight line would just about keep up with an SV650. It had bags of character though, sounded fabulous and just looked stunning in all black. If I could have had two 'main' bikes I'd have kept it, no worries.
2. TT600 - once I'd had the fuelling done, it was a great little bike. Fabulous handling and with enough power to be fun. Rode like a 2-stroke aswell. Comfy, even for a 6'3" bloke like me. Put 12000 hard miles on it in 10 months and it never missed a beat.
3. R1100R - 'my' BMW. I love BM's Roadsters, and I had another one of these back in '98 which converted me to the brand. Always had a soft spot for them.
4. Sprint RS - great motor, solid stable handling with excellent (as usual) Trumpet brakes. Bit dull to look at but a worthy, underrated motorcycle. This has been a tie with the BoxerCup Rep which is my current bike. The BM's big, gruff, and quirkily handsome, vibrates a bit but is a bike I know almost inside-out having owned a few of them now. Excellent long-distance machine.
6. HD Streetrod - gorgeous motor, amazing brakes (especially as the bike weighs nigh-on 300kg) and very stable, slow-steering handling. Trouble is it was very uncomfortable, drank fuel like it was going out of fashion (rag the titis off it and it'll only do 30mpg) and was just too much like hard work to ride quickly. Although the Dyna had less ground clearance, it probably handled better. Still, on a smooth A-road the Streetrod could cover ground pretty quickly (as a few others found out to their surprise) and the motor's a minor masterpiece.

Ringadingding