So it occured to me this morning, while I was reviewing some documentation that SBS customers might be tempted to install ISA SP1 onto their SBS box.
Let's just say that this doesn't work.
Why you ask? Well, ISA SP1 is already included with SBS SP1 for premium customers. The SBS SP1 ISA sku is slipstreamed with ISA SP1, so you, as an SBS customers should feel special as this is the only place you can get ISA with slipstream SP1. However, if you try to install the ISA SP1, you'll receive the error that ISA isn't installed. This is expected, as the sku guids are the different(basically, some mumbo-jumbo to help us differentiate what's what).
So, bottome line: don't install ISA SP1 on your SBS SP1 premium boxes.