What about VXUP/VXDN?

VXUP is a new etf from Accushares that seeks to provide exposure to the VIX instead of VX futures. VXDN is just its inverse counterpart. I know that they have only been trading for about 5 weeks, but what do you guys think so far?

These two articles discuss the obvious arbitrage opportunity of shorting VXX and going long VXUP:
http://seekingalpha.com/article/3200626-the-fatal-flaws-of-vxup-and-vxdn
http://seekingalpha.com/instablog/10211511-eli-mintz/4020976-the-relation-between-vxup-and-the-vix-futures

The really interesting thing about them is the "Corrective Distribution" that Accushares uses to keep them at their proper values. This is discussed here: http://sixfigureinvesting.com/2015/06/how-does-vxup-vxdn-corrective-distribution-work/

Of course VXUP is very thinly traded, but if it ends up being even moderately liquid, would anyone consider trading it?

I sat down and did the math with a bunch of scenarios on these to see when they were first announced to see if the various mechanisms actually worked. The bottom line is that the rebalancing mechanisms won't do anything to actually rebalance them. One will always trade higher and one lower by an equal amount than the VIX, and that amount will be directly tied to the contango or backwardation of the VIX futures. Occasionally you'll get extra pairs of the two stocks, which will then immediately move to the same discount and premium as before. The reality of this can be seen if you look at the discount and premium of the two under/over NAV now.
If you don't feel like doing the math, then you can always use the more intuitive way to look at any risk free arbitrage opportunity. If this directly tracked the VIX index, then you would have a risk free arbitrage between this pair and the VIX futures. At which point everyone would buy/sell to take advantage of the arbitrage, at which point the arbitrage would go away. This means that either this pair trades at the same (adjusted for the built-in 4.5% roll) discount/premium as the VIX futures or the VIX futures move into a fixed, 4.5% contango to match this pair. Given the microcap status of this pair and the number of futures contracts outstanding, it's easy to see why they've moved to match the futures rather than the other way around.
There will never simultaneously be a product that exactly matches VIX and VIX futures with significant contango/backwardation. If that existed then they would both immediately move to an equilibrium where they were both equal and the arbitrage opportunity would go away.