I've gone 1 down on the front and 4 up on the back.
Don't listen to anyone who says you won't notice much difference: it pulls away like a rocket. I'm all about acceleration and I love the combination.
But yes, it does reduce your top speed. But here in New Zealand, fastest we're legally allowed to go is 100 kph / 60 mph so I'm still nowhere near hitting the limit with this combination.
A couple of things to bear in mind:
1/ 1 tooth down on the front is equivalent to 3 teeth up on the rear
2/ personally I've always followed the rule that you change front cog, rear cog and chain at the same time otherwise you expedite the wear
3/ if you go more than 1 down on the front then you run the risk of increasing the cog and chain wear as the angle of attach becomes quite fierce
4/ if you go much bigger than my 52 tooth cog on the rear you might start to have problems keeping the front down (especially if you do the 1/4 turn throttle mod ... which is next on my list)
5/ while my combination may be less economical than the stock, it still spanks my V8 Audi S4 for mileage!
6/ chicks riding pillion really "appreciate" the higher revs
Check out
http://www.gearingcommander.com/ for a cool tool that calculates speeds / revs / gears etc., ... depending on you bike and the mods you want to make.
Good luck - let us know what you finally decide and what you think of it.