...it turns out, three teeth do make a difference!
I've only taken it out for a short spin, but I consider the new sprocket an improvement over the previous one.
The engine no longer feels like it's about to spin out of control if you get a bit too nonchalant with the throttle; instead, acceleration is, how can I put it, meatier. Of course it's not as quick off the mark as before, but it's by no means become slow. The real test will be a longer outing, say 30 or 40 miles, but I think it'll be much better.
My friend Brian confirms I wasn't just imagining an improvement, with this little bit of engineering sorcery...
"Three teeth equal 6% which means 60 revolutions less per 1,000; this quite significantly (as you have sensed already) alters the feel of the bike.
The ultimate test of gearing is the horsepower reading: maximum HP should occur at the moment that friction and air resistance equal HP.
In other words, top gear terminal velocity should occur at the moment of peak HP.
Put another way, if the bike won't go any faster in top gear, this should coincide with peak HP rpm."
Cool huh? Anything that mentions top gear terminal velocity is bound to be good : )