I have a Zoom G1u that I'm really happy with. My favorite guitar accessory, actually. According to Zoom's website the G2.1Nu is the same thing but better, so even though I don't have experience with the G2.1Nu, based on how good the G1u is I could say that it should be amazing.
Had one once, POS compaired to my PocketPod.
Save your money for a PodHD or maybes an Eleven Rack or Axe FX if you dare!!!