Win7/Server 2008 R2 sp1 is on Technet and MSDN today.
Q. Will there be a slipstream version of SBS 2011 that has sp1?
A. I don’t anticipate one at this time.
Q. Can I slipstream it to SBS 2011?
A. Nope. Due to the intergrated install, no can do.
Q. Should be installing it at this time?
A. While it’s fully supported…. I’d not be rushing out the first day on a production system to install this. SP1 goodness is really in HyperV, not in the base OS.
Q. If I have HyperV should I install this now?
A. Again, in test yes, Production not quite yet. Also some argue that you want to clean install and just rebuild your HyperV servers underneath.