I am working with an MSP customer who received the GA announcement for r17 just after I'd finished migrating them from 12.7 to 14.1.03 in DEV. I did a trial migration on a sandbox and showed them the outcome and they were happy to proceed to r17. Since I had already successfully merged their extensive customisations from 12 to 14.1, the upgrade from 14.1 to r17 has been almost trivial. There appear to be minimal changes in the HTMPL between 14.1.03 and 17, so there was very little rework involved.
I've also recently taken a smaller (and much less customised) client from r12.6 direct to r17, again with no significant issues. Tell them to go for it :-).
Regards,
James