Got to try out the UA Lion today, through a pair of Genelec 8040 studio monitors which are similar to the Genelec M040 models I use at home.
The good: The UA Lion sounds like a good Marshall amp sim, responds nicely, good cabs. Soundwise not much to complain.
The bad: To me it does very little you can't get out of a Strymon Iridium + 3rd party IRs. While the Strymon does not have the individual channel volume controls or a boost and its room reverb is a bit different, the end results can be very similar. So I'd rather buy the more flexible Strymon.
The ugly: All the usual UA stuff, like the mobile app, lack of MIDI, single preset etc.