Congratulations!
"must have" stuff... that's the fun part of the wait time. As you wander through the camping aisles of your local stores, you look at those items and think to yourself "I 'must have' this <gadget> for the 550"
And then you, like me, start what has been referred to as the 'nesting materials', as you await the birth from the Nest, aka, the Camp-Inn factory floor.
Everyone's nesting materials is different; for some, it's simply consolidating all of their existing camping materials; for others, it's getting teardrop- or camping-themed bedding for the cabin, and towels for the galley. Some people pick a theme, and run with it! everyone is different on their 'must have'; but I think just about everyone succumbs to the 'gathering of the nesting material' in some fashion. Feel free to share your nesting material during your wait period.
I'll tell you 1 of the things I 'had to have' while I waited--identical french press and thermos mugs for the 550... even though I already had those exact ones in the house. Simply so they can be stored in the galley and not shuffled from kitchen to galley when going camping.