Like everyone has said I also recommend just buying a handfull of jets in the general range of what you'll need based on your mods. Once dialed in you will have to change the main from winter to summer, but it won't be guesswork....you just go bigger when it gets colder, and you can tell by how it's running. It's real easy to know when you need to go down once it gets warmer as the throttle response will suck when it gets warm out after winter.
The only good thing about a 'jet kit' that I've ever seen is a friend that has one (not sure which brand) got this rubber case thingy to hold all the jets in and it also has a Thandle wrench for the jets that stays in the little rubber case thingy. I'm sure he paid way too much for it though. I just keep my jets in an old pill bottle.