Ted,
Used a Psion 5 at uni to good effect. Write notes/essays at beach/pub/airfield then put them back on yr PC ast home. I don't think a keyboard much smaller than a S5 would work for proper stuff. Also, aklthough a gimmick, the dictaphone is very handy, especially for library ref.s, and phone numbers etc in aforementioned pub...
Also feels a lot more solid than a Revo, and you can change the batteries if they go flat when you're away.
Don't buy a 5mx, however, buy an Ericsson mc218, which is exactly the same (even made by Psion), but has ****loads more software, a WAP browser etc, and is generally a more sorted thing. And cheaper too. Got mine from <A HREF="http://www.exportech.com" TARGET="_blank">www.exportech.com</A> in Bournemouth.
You also need a good case - Palmtec.com for these.
Hope this helps.