I'm late to the thread as always, but I do love to add my 2 cents
I do like the chain conversion and am not sorry I did it. I also run the 17/43 at the moment. It's great on the highway. I have 18" ape hangers so my bike isn't exactly streamlined, but it looks cool (IMHO). I installed a nice sigma backlit speedo and it workded great. WOT in 5th I got up to 147.99km/h. Stupid .99, but still not too bad considering the aeirodymics and it will do 125km/h all day and it doesn't sound like it's going to explode. In the city however I have a few more issues with this gearing. I like to drive 60km/h in town or often have to, and that's fairly high rev's in 2nd, but it's just too low in 3rd. I find I'm constantly switching between 2nd and 3rd when following someone or doing 70km/h just so I can be confortably in 3rd. I'm going to drop the front to a 16 for a bit, because I do most driving in town right now, and to see the difference. It's AWESOME to be able to switch it up like that, and it was such a great cheap conversion.
Speedo... I hate taking off the sigma speedo at every stop and didn't really like the look of the wire going to the front wheel. ( I have no wires to handlebars, no turn signals etc.). While out I didn't take it off and someone stole the little gadget and made the decision to take off the speedo very easy.
I had taken to using the speedo hole in the tank as a drink holder, and had much success carrying plastic bottles. I then thought, why not put my tall can of beer in the hole on the way to poker.... I got sprayed with beer about halfway to the game when the can ruptured. I was very suprised, covered in beer and it cooked onto my engine. Note to self, don't put can's in a hole with somewhat sharp edges!