I am a Picasa user and I’m not very happy with this. Application is terrible (and works under Wine badly) and site is not very convinient too. But I use them since storing photos in Picasa is obvious solution for any Google account holder. For a long time I used some command line uploader I found somewhere on the net, but since 2015 Google dropped support of ClientLogin/OAuth1 in their services, so all of the command line tools (including even GoogleCL created by Google themself) stopped from working.