I find there are a few killer extensions like https://extensions.gnome.org/extension/10/windownavigator/ and https://extensions.gnome.org/extension/60/overlay-icons/. The first one means you aren't forced to grab the mouse in overlay mode (which was my biggest complaint), the second means you have a chance in hell of recognizing what something is when you have more then around 4 windows open.

I like it too, but the big things for me (after stability issues) are

1) the notification area feels not well done. I am constantly triggering it when I don't want to, and I find it is a pain to trigger when I do want it.

2) the search function in overlay mode is really choppy, which is funny because I would consider this a solved problem in gnome (with gnome-do)

I think its a definite improvement over gnome 2, but it probably needs another 2-3 years of dev time before things are as polished as what you would expect nowadays.