If you choose to do the server, it would probably be a permanent install and I might consider calling AC to schedule an install. They will probably help you even though you have not bought the program.
Lowell,
I agree with everything Wendell says, as I usually do. If you want to write a note ten times faster than in most drill down programs, then AC is right for you. If you don't want to pay $5,000, then it is.
I do disagree on installing it on the server. It certainly wouldn't be permanent, and you wouldn't need AC support to uninstall. It would simply be Add/Remove Programs -> uninstall AC, then uninstall SQL Server Express 2005 AC instance. In fact, keeping it on using the excuse it is too difficult to take off would be violating the EULA. But, to play with it, you don't need to network it anyway, and thus, could install it on any computer. But, you do have the option of networking it.