Yeah, specs are not impressing, but real precision is much better. If we assume that my Keithley is in cal (and "calibration certificate" included with my $5 reference is not complete bullshit), then all the meters read virtually the same (see photos). Let's see long-term stability...
I accidentally purchased two 121GW, both read the same. My only complain so far is a little bit slow autoranging (may be I'm spoiled with Keithley) and update rate. The specs say 5 samples/s, but it's more like one update in two seconds or so. I tried to change "logging interval", no changes. Hope it's a software issue.
Also Low Z doesn't work (shows "0.0") until voltage reaches 11V. First bug?
Software version "U-1.01". Sound indicator for wrong leads connection only kicks in when trying to use A/mA ports in voltage mode.
UP: just noticed the thread for reporting bugs. Duplicated my findings there.