VMware released View 5.1 yesterday and it has some changes that require you to pay close attention.   I am going to link and post the highlights here, because its really imperative you know this!

www.vmware.com/support/view51/doc/README.rtf

1)  You cannot downgrade View 5.1 Connection Server to previous versions.

2)  vCenter Server and View Composer hosts need valid SSL certificates.

3)  Security server and View Connection Server hosts need valid SSL certificates. 

4)  Certificates for vCenter Server, View Composer, and View servers must include certificate revocation lists (CRLs).

5)  Windows Firewall with Advanced Security must be enabled on Security Server and View Connection Server hosts. 

6)  Back-end firewalls must be set up to support IPsec.

7)  View Clients must use HTTPS to connect to View.

8)  Encrypted and cleansed View backups require new restore steps. 

9)  Before you can upgrade or reinstall a View 5.1 security server, you must remove the relevant IPsec rules from the paired View Connection Server instance so that fresh rules can be established.

This is a pretty big deal.  I have seen a few people talking about this, but most posts are focused on new features.  Please read the linked document before you upgrade.  I will be upgrading my lab as soon as EMC world is over and will post my experiences right here.