This is needed tbh. OS X El Capitan beta 1 and 2 were great on my retina Mac: no graphical glitches, very fluid, and apart from small bugs, it was very stable. I immediately upgraded from Yosemite which I pretty much hated along its life cycle due to many persistent bugs (slow UI, Wi-Fi issues, etc).
With the introduction of beta 3, it felt like I was back on an early beta of Yosemite with more features. Dock glitching, screen flickering on boot, finder sidebar doesn't remember size or positioning, just a huge mess. Beta 4 fixed some bugs yet completed destroyed the frame buffer. I couldn't even look at images in preview in full screen without a dark big horizontal block showing up on the left side of the screen, every single time.
I don't even know whether Apple are actively testing what they put out, but these last two betas have been a huge regression. It's been so bad that if beta 2 had been the GM of El Capitan (hypothetically), it would be a fantastic release.