It is symbian 3 so Nokia will pack it with as much as they can to sell the device and you should already know that symbian is a much more mature WORKING platform than the 900 has got.
My E90 had office and everything worked including talking GPS, many examples can be got from symbian and as for flash, it will obviously have the latest version compatible with the hardware within the device.
Browser will have also the latest version but as to performance over the 900 we have to wait and see but you cannot knock something that's not publicly released yet.