I've been intrigued by the 7 VAR a few times, might still happen. The gap in power and bullet weight above the 6.8spc, 6x6.8, 6WOA, 6.5Grendel, 243LBC, etc does tempt me. The data I've seen puts the Valkyrie somewhere 100-150fps behind the 7-08 with the same bullet, at least in factory ammo. Hand rolled 7-08's can run away from the Valkyrie.
The disadvantage I've seen so far, besides making brass of course, is the barrel length needed to get the velocity. Much of the data available for the Valkyrie right now looks great - until you realize it's from a 24" or 26" barrel, instead of the 20 or 22" barrels common for 7-08's. In short barrels, it seems to rank about the same as the Grendel or SPC cartridges.