Can't help you on the AlphaSmart, but when it comes to the eMate, the biggest problem I've run into is getting my writing off of the thing. I don't know of any programs that will allow you to transfer the text you create on a eMate to another machine for editing, etc. You can send the file over, sure, but you can't open it.
If anyone knows how to do this, please let us know.
That said, the eMate is a very cool little machine, and an excellent alternative to a laptop is all you want to do is write.