@mergen3107:
If you intend to work on JARs or upstart services that *may* throw you into a boot loop (or if you just like the safety net), and are okay with working over SSH in diags, then basically, yes, ASAP (ideally, after having familiarized yourself with how USBNet works

).
You'll generally always want RP+CRP together.
And while RP does some persistent changes to the diags partition, the "trigger" bit is like any other hacks, it will get wiped by a FW update.
(As for your SSH at boot question: it depends. It may help with *some* type of boot loops, *if* you're quick enough, but not for others. While RP+CRP should be able to get you out of more potential pickles

).