Not that I regretted upgrading, but a few weeks ago I was forced to do a clean install and thought I'd rather go with Mavericks in case the issue I experienced was related to Yosemite. As it turns out, it seems it might have been related but anyway. Since downgrading, I couldn't be happier, the whole OS X experience is better in 10.9.5 plain and simple. It made me realize that besides the new UI, any of the new features in Yosemite is something I don't need. I don't need to make calls on my Mac, I don't need handoff, continuity. But I need speed and stability. It would be unfair to critize 10.10 on stability, as it was, for me at least, pretty solid - but speed.... Finder, Safari for example, slow in the case of the Finder, and awfully slow in the case of Safari 8.
I couldn't say I regretted it (I thought performance would improve over time), but now that I'm back to 10.9.5, I've clearly seen the difference, and I certainly don't regret downgrading.
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I haven't really noticed a difference. No real slow-downs, went in and tweaked a few things (Dark Mode rules!), just a few bugs here and there.
nahh hopefully you won't get anything from any side - good for you and glad you have working as you need.