As a dropbog alternative, I use Live Mesh from MSFT - 5GB storage and possibility to sync more folders.
Regarding the Google offer: It seems to me that the storage can be (currently) used only for photos (picasaweb) and gmail. It doesn't look bad, but I would still prefer to pay price for bandwidth per year. If I have to use this as a backup for all my photos in original res., 20GB is not enough, so the Flickr's unlimited storage for $25 still looks better.
For me, the OK price would be $5-$10 per 20GB upload bandwidth/year.