I just fired up Galaxy for the first time and weeks and noticed one of the previously greyed out "Features", the In-Game Overlay, is now checked as enabled. How does one access this overlay? Is it even really functional?

I don't think it is, but this is a game-breaker for me. It was agreed Galaxy would not interfere with the game once it is running.

For installation and update only...

It can be turned off, just like most other features of Galaxy. If you want, you can strip it down enough so that all it does is install and update your games, but if you like to use other features, you can turn them on or off as you like.

Why is it a game-breaker if you can disable it?

This is what they say for Steam-Client as well, you can turn off notification but the overlay still messes with the game.

Also, I usually distrust companies and once the feature in implemented as sneaky as the option to turn if off appeared, it can disappear.

You can turn off the overlay in Steam as well. Just because you haven't figured out how to configure these clients to your liking does not make them or the people who make them untrustworthy.

They are working on a game overlay however the feature does not exist in the client yet however GOG has mentioned several times in the official beta thread that an overlay feature will exist in a future build but have not committed to a specific build or date. There is a non-operable checkbox for it in the configuration which is a developmental oversight that is safely ignored for now.

The Steam client also doesn't allow you to turn off auto-updates, while the Galaxy client is said that it will allow you to do so, along with the ability to go back to a previous update. Just because one client works one way, doesn't mean that the other will work the same way; it might be better, or it might be worse. The only thing that you can do is try it and judge for yourself.

I know all this, I have been using Galaxy since the late alpha and the overlay is something that we all knew was coming. The difference now is the previously non-functional checkbox to enable or disable the overaly is now functional. The rest of the Features checkboxes are still non functional.

steam client is very very bad :D, i use steam very rarely and when you 'play' a game its always like its 'lagging'
all that steam client overlay stuff is most certainly not improving nor optimising the game experience.
no matter how fast the pc is, if your gaming the game exe should be the one thing thats running.
Any process that runs require cpu and resources.

If this is where they want to go, it's fine with me but I won't use it any more.

I wasn't following the Galaxy Beta thread closely and it doesn't matter to me when I found out about it.

Yep, you are very correct sir. :)

I for one can't wait for the overlay, anyone complaining about features that can or will be able to disable is being ridiculous.

By default I launch my GOG games via GOG Galaxy nowadays right up until the first time I want to take a screenshot or know what the current frames per second are, or to access a web browser while the game is running but the game crashes or otherwise misbehaves if I ALT-TAB out of it (most DOSbox games and others), or when I decide I want to broadcast video of my game to a friend I'm talking to on the phone or something. Whenever any of those situations arises, I switch to the next best solution on deck which for me is to set up a non-steam game shortcut in Steam. I already have Steam so I don't have to install any additional 3rd party software, and it has all of those features built in so it's an easy substitute launcher. The drawbacks are losing Galaxy time tracking which does not actually work anyway, and my Galaxy game activity status being inaccurate but nobody really looks at that stuff currently anyway.

Soon as the overlay is there though, if it has working features that satiate my need(s) I'll forgo the Steam launcher links unless I need video broadcasting. I doubt GOG will add video broadcasting for quite some time though if ever as that'll be a hell of a lot of work to do I suspect, and I think only Steam offers that feature integrated currently. Technically I could use a third party app for that, but there are none that are free and unrestricted that do what I want so it's easier for me to just use Steam broadcasting in that case for now.

I imagine the overlay must be on their top 5 list of important features to get out the door though.

Well all you have to do is disable the overlay in the options, then it won't interfere with your game.