If you need the machine now for production, I would go ahead and take the loaner. That is if your conformable installing the spindle. Otherwise waiting a few weeks might not be a bad idea. At least shopbot is pretty up front with delays, and they don't leave you in the dark wondering.
My machine was delayed about a week, due to the thanksgiving holiday. They were pretty honest about that, and were very apologetic.
If you haven't already I would take advantage of the extra time and make sure that electrical, and dust collection are in place. You will probably also want to build a stand for your control PC, and setup some kind of extra storage for tooling, as your collection will rapidly grow.
I would also pick up some MDF, and Plywood for the spoil board, and various other fixtures you will end up making.
After I spent 4 days assembling my PRS Standard 48x96 I had to wait another 5 to get an electrician to come out since they were either busy, unwilling to work on a weekend, or afraid touch anything that had anything to do with CNC equipment.
Michael Schwartz - Waitsfield VT
Shopbot prs standard 48x96. Aspire. SB Link.