>Is this for Clients AND Server?
>Are most people planning on upgrading to 5.1?
>What are the implications of staying at 4.2 or lower?
>
>Is there any additional cost to upgrade?

V4 clients are supported with the v5 server but you will want to
upgrade to the v5 client to take advantage of the bug fixes and new
features.

Many folks have already upgraded to v5.  The current level is 5.1.5.  I
assume that if people are continuing to run TSM they have or will
upgrade.

The implication of staying at v4 is that you are running a mission
critical business process with no vendor support.

Yes, there is an upgrade cost.

David