This second generation of the Acer Predator X34 was just released in January. It has a handful of improvements over the original X34 (non "P") model such as native 100Hz with OC to 120Hz instead of 60Hz/100Hz, a more aggressive 1900R curve, thinner bezel, lighter weight, better OSD menu controls, presumably better QC, etc.
IMO this is the best ultrawide available, the only thing comparable in specs is the Alienware AW3418DW but this is a brand new model. I received mine yesterday after researching for weeks and it's stunning; pixel perfect and a significant improvement over my respectable U3415W. It's so new that reviews are still pretty scarce but here's one from Techspot [techspot.com]
Use promo code EMCPRPV44 for $100 off making it $999.99 at Newegg [newegg.com]
with free shipping.