So, I'm pretty late to this discussion about whether we can replace our low-tech gear with high-tech toys.
In environmental consulting, most fieldwork is low-tech. That's not necessarily true for all field people or all geologists; I'm just going on my experience here. With that caveat out of the way...
I could carry around a tablet PC for notes, or I could use an ipod app instead of a physical compass. I don't, and most consultants I know don't either, for a couple of reasons:
1. Equipment fragility. If it's below freezing or above 90, or if the humidity's high, a lot of electronic gizmos have problems. I just dropped my rugged cell phone a few minutes before starting to write this post, and the battery popped out (still works!). The screen has a few dings from being dropped on hard surfaces, and it's only a matter of time before I drop it in water. Finally, if you're in a particularly nasty place, you may need your electronic equipment to be intrinsically safe.
2. Legal documentation. Most regulators and lawyers like to see one field original, in ink. Yeah, you can gin up an electronic signature for your files, but most authorities are most comfortable with a stack of paperwork that can be stamped and filed and tucked away.
3. Incompatibility. PDFs are the gold standard right now for transmitting reports, so this is going away. But you still have relic filing/storage issues. Floppies? (even real floppies)...zip drives? Various drawing programs that have been rendered obsolete? A lot of scientific data retain value for decades. It's nice to put stuff on a network (and how good is your backup, anyway?), but nicer still to retain originals for posterity.