So far everything seems to be working well with BIAB '15 and 10.10.4 on my system, although it's only been one day.
I'm not sure if it's my imagination (or just all the caches being cleared with the update) but .4 seems to be running a little quicker and smoother than .3 did so far.

I would say go for it, be sure to back up first though (just in case).
Hopefully this helps.

- Jay


MacPro 5,1/12 core@3.46GHz -- OS X 10.15.7 -- ATI 7970 -- 32 Gig RAM -- Crucial 500GB OS SSD -- Samsung EVO 1TB Audio/Sample SSD -- BIAB 2024 -- Logic Pro X -- Cubase Elements 14 -- Too many plugins