Have you been having issues with Steam recently since the new Library Beta? This latest Beta update should make it a much better experience.
The newer Library (and Friends UI) are a bit heavier on your PC, as a lot of people noticed. However, you can enable GPU acceleration to make everything quite a bit smoother. That came at a cost though, as there was an unfurtunate memory leak and it sucked away performance from gaming. Valve have made attempts to address these issues in the new Beta update out.
Now the Library should be prevented from doing stuff on the GPU when the Library window is covered up, a memory leak was fixed if GPU Acceleration was turned on, some Library animations don't run if the Steam window doesn't have focus, the Library failing to load if you have a lot of non-Steam games was fixed and they also adjusted the GPU Acceleration to default on for Linux and Mac.
However, there's still a few issues they need to solve. For me, updating to this version with GPU Acceleration turned on caused my Library to not even load at all. Steam just became unresponsive when I tried. Going onto the Store worked, Collections sort of worked but the Library Home wouldn't load. Reloading Steam again seemed to fix it though. Twitchy, but okay now? Seems someone else reported a bug on that.
Another issue I've seen, is that when I ALT+TAB with a traditional full-screen game running I can no longer seem to interact with the Library—that's a bit of a woops from Valve. I've reported this one.
Just for Linux, they also updated the Steam Runtime. It now disables the obsolete SSLv3 in libcurl which should fix a problem with libcurl on Arch Linux. They also disabled LDAP in libcurl and updated SDL 2.
Release notes can be found here.