Better, but bugs and compatibility issues are inevitable

Is already much has improved. Minimizing windows in your program icon, the display of minimized windows in Exposé, the ability to tap the start of a window title in Exposé and thus select the window (who wants to use mouse CC) and many other small details. Moreover OpenCL and improved multicore support, although I on my Mac since not so much supported by notice because of its graphics card no OpenCL C.
However, chances are that some programs are not quite compatible. Was with me with Firefox so, the times crashed often, but this has put back for an update. So small utilities like DynDNS Updater are still waiting for an update that makes it again be viable and if one uses exotic things like Macports, you also have some problems is there with with some probability.
Great new bugs there are, as an animation technically somewhat confused acting Spaces (animations are so important !! 1) and - probably purely anecdotal and debt by Verhunzung the previous Leopard system - an often times entering crash coreservicesd what then a painful has pseudo crash of the whole system result. In this respect one can probably recommend a clean installation and no-place update on Leopard. Or PRAM reset. Oh moment, that never helps yes.

All in all: An important step towards full 64Bitisierung the Mac and many small improvements, which however can be Verschlimmbesserungen part if a an eventual old behavior has grown fond (Exposé shows the application mode all application windows from all Spaces for example). But Snow Leopard operating system name ... is still great. Buy and may first be let in the closet.