I've only picked up the Van Saar set so far but I have to say I find most of the new Necromunda stuff (both GW & Forgeworld) really quite cool.
I've already got my sights set on a few more of the kits for some Imperial Guard conversions and hoping for plenty more good stuff to come. The new Delaque guys are really pretty creepy - old Delaque used to look like burly bald guys in trenchcoats, these new guys look more like Hellraiser! Really quite unsettling if you stare at them a little too long... Van Saar and Orlock are cool, Escher are very Harley-Quinn (but then again they always were), I've seen a lot of conversions with the Cawdor gang into Empire and Bretonnians, Goliaths don't interest me, Enforcers are pseudo space marines but do offer a lot of potential for expansion of my Guard.
The only downside I find with them and some of the other new GW sets I've had recently is the fixed poses. I like that they are quite dynamic and interesting but when you get a set of 10 figures you really only get 2x 5 poses and it's only the changes in head and equipment that sets the figures apart once built. Necromunda isn't too bad for this given that you have lots of options for weapons but the other set I had was the new Sisters of Battle and again, they basically came as a set of 10 fixed poses with maybe 2-3 options for different gear for each - they were even designed to the point where arm sockets would only fit into certain bodies so not a lot of scope for customization unless you get a bit creative.