Hmm, I did another benchmark on a more typical folder of jpgs and avis from a digital camera (217 files, 2007-06 folder) and the benchmarks were:
one at a time: 1m 30s
batch mode: 1m 10s
which suggests there is not that much to be gained by a daemon mode. I'm a little puzzled why this folder shows much less improvement than the other one, which had a strange mix of raw/tiff/jpg/pdf/other files... I guess more research is needed before bothering with daemons.