I've been very happy with Picasa over the last few months of using it. The new version which is still free has added suppot for attaching captions to the image in the EXIF data.
I would be great if Pbase allowed you to apply this EXIF caption to the image label. Then you would only have to label the images once and you could do it offline.
The is likely a BIG matter of opinion but I think that Picassa is currently the best free Windows image managment solution out there. It would be great to see it work really well with Pbase.