I got a Compaq Ipaq 3955 a year or so ago before I had a notebook computer, and for the purposes you mention, I think a Pocket PC can work fairly well. However, I do find I use it less and less now that I've got a notebook computer.

PowerPoint: If all you're doing is playing PowerPoint presentations, then it should be fine. As noted, you should have the .ppt file on a thumb drive for transfer to another machine in the event of "technical difficulties". I wouldn't use a PDA to author/edit a PowerPoint presentation - at least not one that's complicated in any way.

Word, E-Mail: Reading Word documents and e-mail is o.k. It's not great if the Word document has lots of formatting or if its very long. Same goes for e-mail. Authoring/Editing documents is o.k. as long as you're not doing any fancy formatting.

Adobe PDF: PDFs are a pain on a PDA. If you make them big enough to read, you're forever scrolling up/down and side/side. Ugh.