DO IT NOW
Rode the bike in to work this morning, and its like a different bike to ride. The first noticeable benefit is low speed work and pulling away. The whole process is definately smoother. The bike will now trickle along in first gear with minimal revs, no clutch banging (!) or manual clutch slipping required. Ideal for town work.
Acceleration is better, although with it still being wet and lots of traffic I wasn't able to do any proper 1st/2nd gear full on acceleration, but still felt a bit quicker.
Top gear work, at about 70/80 is much easier as well. The bike feels much more responsive when I open the throttle to get a move on ie no need to change down to 5th to five instant drive - much better.
Overall its definately a worthwhile mod. The sprocket doesn't cost much and it only takes an hour to do, if that. I can post some more detailed step by step instructions about how I did it if anyone is interested or wants to do it but is feeling hesitant.
cheers,
Ben