Disadvantages:
It wont run any 16 bit software
True
There will be some applications that wont work properly
Its very short, still some issues with winar and winzip even with the 64 bit versions and explorer.exe, but most things work now.
Driver support for external peripherals such as printers, scanners and webcams is still pretty thin on the ground
It is silly, my wireless MICROSOFT mouse doesnt have drivers so i cant use the tilt wheel, how stupid is that!
Still not very many AV vendors that support it
I think its at decent levels now
Advantages:
Support for amounts of memory larger than 4GB
It runs really smooth with 2 gig.
No longer a 2GB per process memory limitation
The only thing that still runs crap in terms of running processes is windows explorer(explorer.exe) i swear it has a memory leak, it gets bigger and bigger. End task and restart sorts it, but its a pain.
Most 32 bit applications work
More and more have a 64bit version now
Most of the games that I tried worked
Worst i have had was battlefield 2 saying its not been tested, thats it.