Pros:
Feel more comfortable if you're short
helps with keeping the front wheel down due to power
great for drag racing
totally reversible if you don't like it being lowered
not being able to wheelie as easily
Cons:
you will have less lean angle in curves because your lower fairing will scrape (if you ride aggressively which is like 120 in a sweeping off ramp)
If front and rear aren't lowered correctly, you would feel like you're riding a Harley and steer heavy
lowering too much will cause you to scrape or bottom out on big bumps
you will get bitched at by the track riders "Why would you do such a thing"
not being able to wheelie as easily
I have 3 zx10's, 2 of them are lowered and one is stock height. I'm not that tall and I enjoy riding the lowered ones more than my stock height one. There's not much that you lose as far as cornering if you lower the front and rear correctly. I love the fact that I can hit it a little harder without the worry of the front wheel coming up. A ton will say there is a big difference, but I don't have the lowered bike on a road course to feel the difference between them to prevent me from keeping them lower.
As for how to do it. Here are 2 threads of mine.
Lowering links.
http://www.zx-10r.net/forum/showthread.php?t=78161
and you can also shave your seat to save you about 2 inches
http://www.zx-10r.net/forum/showthread.php?t=71586