This might be useful:
What I use Picasa for:
- Managing the snapshots (odd bits and pieces) on my C drive, prob about 2,000 or so
- Receiving export processed by Lightroom, uploading to Blogger (blog) or Picasa (YACF, others)
- quick crop, resizing & eMailing
- Slideshow for showing photos on screen
- capture of screen capture
What I use Lightroom for:
- Importing photos from source (Picasa will, LR does it better)
- Organising online photo collection (c 55,000)
- Organising offline photo collection (c50,000 )
- Photo processing workflow, including watermarking. Noise removal, curve editing, white balance, channel balance, sharpening, graduated effects, etc etc etc Creation of presets, amazing range for B&W control. Non-destructive, lets you walk history.