Licensing: per processor vs per user

Wow, licensing always a touchy subject.  However I will givey ou my thoughts.

First and I am sure you have heard this one before answering the question about how much can a server handle is virtually impossible.  way too many variables with the types of processes that are being used, the type of disk, what else may be running on the server etc. 

Now for the CPU vs user conversation i have found that it is more usefull to not think in terms of how many users per process or the like.  Rather do you need the flexibility that going per user can give.  If I have a good testing environment, QA, UAT, sandbox etc etc.  and I have disaster recovery needs, or geographical dispersion and so on and so on.  I wouldl LOVE the flexibility that going per user gives me.  Or even if i woud love to have that flexibility.  Then as my organization changes, our use of the product may evolve etc, I have the ultimate flexibility to add more servers, move servers, etc.

Thoughts?  I would love to hear other opinions