In my opinion, the 2100 is not a consideration. It still doesn't have hard drive, and it still doesn't have the OS in RAM, so it can't be upgraded by software.
The registrations still are harder to get to. The endings and intros variations still have only one button each, so must be manually selected each time you use the style, unless you resave the entire style to memory. The onboard memory is still insufficient. The keys are still very light in weight. There is still no video out. (I THINK the Tyros has this).
I think the Tyros sounds far better than the 9000 or 2000. The drums are much more alive.
The styles are better, even the ones that are basically the same have been redone to sound better, and there are a lot more styles on board, and a lot more space to for your own styles. The polyphony is much greater on the Tyros. The buttons are larger and light up. The display is larger and easier to see. Much more.
On top of all this, the 2100 will most likely not be available in the U. S. much before 2004, if Yamaha follows their usual timetable.
No 2100 for me.
DonM