NewtOS2.1 is much more "complete," and oh how I wish it were still being developed — but the early Newtons and the first Newton OS do have a certain charm about them.
I have a 110 here in the collection, and could easily see using it as an organizer etc. were it not for the fact that I have a 2100 in daily use. I have occasionally been tempted to revert to the 110, however, since the 110 is smaller and simpler. I also find NewtOS v.1 handwriting recognition engine (for printed characters) to be pretty darned accurate, and fast enough to be perfectly usable.
Cursive handwriting, though? Forget about it.