From IBM (Smartsuite owners):
"While no major compatibility issues have been reported when running SmartSuite or Organizer on the Vista 32-bit (x86) version, these applications are not supported by IBM/Lotus Product Development on the Vista platform"
Now I have read of a few minor issues, but I think it was with Approach. There may be slight issues with 123, but from what I've found out, nothing too drastic.
You certainly shouldn't break anything by installing and trying it.