My personal experience:
- I had to redo the perceived output level balancing for all my presets
- One or two amp models had to be further tweaked (had a gain structure just at the edge of breakup in v17.04 and ended up with full distortion in v18beta). It was easy to tame it back down.
If I had to do it again, I would wait until the official release. It's just too time-consuming to readjust all levels at every f/w upgrade. Note that this isn't a complaint... it was my decision to jump in while still in beta (I wanted the two new factory IRs from cvab pack 8). But like I said, in hindsight, if I went back in time, I would wait until the official release (but... would I be *able* to wait?!?)