Lightroom can handle the editing part, but the Picasa plugin works as a publish service, not full two-way album management.

What that means:

• Lightroom edits photos in its own catalog/workflow.
• The Picasa plugin publishes exported versions from Lightroom to Picasa Web Albums.
• If you later change a photo in Lightroom, it can be marked for re-publishing so the updated version is sent again.
• The plugin may support importing comments to some extent.

The main limitation is with photos already uploaded to Picasa by some other method: Lightroom/the plugin generally won’t automatically know about or manage those as if they were originally published from Lightroom.

So the practical workflow is:

1. Import and manage the photos in Lightroom.
2. Edit them in Lightroom.
3. Create/use a Picasa publish service album.
4. Publish and re-publish changes from Lightroom going forward.

If your goal is seamless browsing of all existing Picasa albums and overwriting previously uploaded images while preserving comments in every case, the answers suggest Lightroom does not fully provide that. The best-supported approach is to start using Lightroom plus the Picasa publish plugin for future uploads.