Any advice on serving out large Powerpoints over AFP?

If you set up users as mobile users they will have a mobile home instead of a network home. The difference is that a mobile home exists on the local hdd of the client and is synced back to the server at regular intervals. The sync only syncs up the changes reducing network usage. This also has the benifit of allowing people to continue to work with their files in the event of a network or server outage.

Otherwise the users have network homes which are read directly from the server like any other network share. Every read and write will cross the network.

i agree with 0racle

mobile profiles is the way to go, i have had no problems with it.

Don't rush into Mobile Homes, its a great solution to your described problem but can be a headache to implement and requires some user education.

Are the clients using multiple computers or always the same one? If they are on multiple computers you will end up creating a mobile account on each computer they use, exponentially increasing the potential for conflicts, not too mention the wasted hard disk space. 10.5 server has some interesting controls for mobile account expiration that may be worth looking into. All of my mobile accounts are on 10.4.11 currently.

IIRC NFS is quick & dirty network sharing without security (either via subnet or "world"). It doesn't look at ACL's etc.
AFP OTOH is dependent on ownership and permissions, often stored in some form of networked directory structure.

In my experience: the safer and more customizable >>> the slower, therefore... the faster >>> more unsafe less customizable.

It's all about priorities.

We use the Shared folder locally when working on larger than large files. Not so much Powerpoint... ours are related to video editing. I'm not sure of how your machines are set up and if they are at a desk or they travel... but we trained our 2500 users under OD to move the file to the local shared folder, then move it back when done. The transfer takes no time at all. Sometimes we use USB drives as well. Next year larger files will be able to be worked on when we get Gig to the desktop... but even then it's better to work locally.