I've tried Rocksmith+ beta now a few times.
Starting the game.... today it was the easiest, only one crash and one restart before sound was working, more or less...
after trying to set the input type there was now a fun, about 0.7 second delay, between plucking a string and getting sounds out of the speakers. (going through the settings a few times more it stopped finally crackling like a little kid playing with plastic candy wrapping.
Until now I could get it to work rarely with the original tone cable, every update or attempt later requires an complet sound settings redo... and I am lucky if it works within 5-10 attempts.
Setting the right output is also a pain in the ***. because getting there needs to go though the input setting.....
with the RT cable and the windows default it has been never more then almost acceptable.
With a Behringer UM2 (= just a plain usb soundcard) it couldn't detect the bass, until I gave up.
With a Behringer UMC1820 it can be used as output, but it is not usable as input. Not with the Behringer own asio-drivers, not as a "single input"as windows offers, not with asio4all. having only the output channels available as inputs will not work... (something like electronics are directional)
With today's supprise of a more than 650ms sound lag on the bass (it's 8ms in reaper) the game has become unplayable.
Even Rocksmith 2014 works perfect with all these options, compared to rocksmith+ (and it isn't really,)
And yes I haven't tried the mobile option, that would mean having to play through the speakers, recording that, and that's something I can't do in this apartment.
These problems alone will not motivate me to try again (I will wait for one more patch to give up finally)
an another big issue is the awful small and disappointing choice for bass players. There is no music that motivates me to start RS+
TLDR:
it's a pain to have to go multiple times through the settings/restarting the game to be able to have a almost working sound, and the choice of songs for bass is at best "not my taste" and awful small.