Ohmygoodness, what a tough question! Well, I agree about the collabs for all the reasons given above.
As to my all time favourite kit by a single designer: *Journal Me This Bits* by Studio4 Designworks
As for Art Journalling, my favourite is: *Sailing New Seas* by Artistic Alliance
Proudly creating for Godigitalscrapbooking, Digidesignresort, Nydia's Scraps,
JanetB Designs, Studio4 Designworks, StarSongStudio, Les idées de Christine