I am about 5'10" and wear Xelement riding boots which have about a 1.5" heel. When I come to a complete stop, I can put both my feet totally down, heels and toes, and actually lift my butt off the seat an inch or two. There is plenty of room for me to wiggle the bike between my thighs. If you find that you want a lower seat height, go for an aftermarket seat like a Mustang, as it sits you lower in the bike and will give you at least another half inch or so.
As for the weight of the bike and center of gravity, I can tell you that my learner bike is a 1980 Honda CB650 and while it was a great learning bike, it had a much higher center of gravity than the Meanie does. I looked it up once and the CB was about 520 lbs dry, which is about 100 less than the Mean Streak, but because of its shorter wheelbase and higher center of gravity, that bike felt heavier. The Mean Streak has a very low seat height, and a long wheelbase which stretches out the weight over the whole distance of the bike.
I am sure you've read reviews of people saying how well the Mean Streak handles, and this is largely in part to the setup of the bike. While it is a 620+ lb bike and definitely not a lightweight, it does not show it when riding. At 5'9" if you do like I do and get a set of good riding boots, you should have absolutely no problem handling it.
As with any bike, just take your time, get used to it, and do some practice figure 8s and panic stops in an empty parking lot til you get completely used to the bike and you'll have a long enjoying summer ahead of you!
