Just found out via Google Operating System that there is a Linux version of Picasa. Looks like it is available for quite some time now (since 2006) but isn't mentioned at all on the Picasa website.
Installation was simple - Picasa is available as .deb - and just after the download I learned from the FAQ that there's even an apt-repository.
First impression: looks exactly like the Windows version (no wonder as Wine, together with Mozilla, is mentioned as used open source project - and Google contributed quite some patches to it)
Picasa is now importing our ~38000 pictures from the hard disk...