Electronic field notebooks: useful, or pain in the posterior?

The UJ mapping class this year were piloting electronic field notebooks, with each group being given a PDA in which they could enter a locality, a description, and any structural data they were measuring. Especially with the structual data, this may seem like a useful innovation which saves hours of tedious data entry when you’re back home. Still, I remain to be convinced that using an electronic notebook is automatically a good thing; the batteries don’t run out when you’re using pen and paper, and there’s also the fact that fieldwork is not kind to delicate electronics (for example, whilst I’m sampling for palaeomag, there’s a lot of mud flying about, including all over me, and I doubt this interacts too well with computery stuff)
I’d be interested to know if anyone else has experiences in using such devices in the field, either in an educational or research context, and what your thoughts are on their usefulness (or lack thereof). Does the extra functionality make it any more useful than a basic (and more rugged) GPS?