I was faced with essentially the same decision regarding wheel choice. All the ones listed already seemed great - and maybe I would have chosen the I9 on 4.2d if I had seen those yummy pics before I ordered....
But I'm a big NoTubes fan so I went with the new ZTR Arch rim (same width as the DT 4.2d), and since Stan doesn't carry my beloved CK ISO hubs anymore, I went with the Hope Pro II hubs - haven't got them yet but hope to be able to give 'em hell soon. The wheelset weight is pretty decent (in the 1600-1700g range) and SHOULD be bombproof for my type of riding. Price is very good - only $650 a set - and Mike at NoTubes is IMHO one of the better wheel builders in North America.
BTW, the XM819 lists at 465g, while the ZTR Arch and DT 4.2d both list at 400g - so for a semi-WW like me, the XM819 didn't seem like a good choice, especially given that the ZTR Arch rim was billed as being for more aggro XC use. Besides, I've not had any problems with my superlight ZTR Olympic 347 rims anyway.
For brakes, I went with Avid Ultimates (currently also own Hope Mono Minis and Marta SLs), since I often swap around wheels rather than change tires - the Avid setup and adjustment is WAY easier than the others. And as a bonus, they are very light and look sexy too!