Loving it so far. I'd long been a fan of the Great Suspender in Chrome, which offers similar functionality (may well be the inspiration for this one). I dropped from Opera using 1.3g to 500m, upon suspending all tabs. And it seems to leave them suspended on restart of Opera, which is great.
So those of us who like many tabs can do it without the memory squeeze. Now we need only deal with the people who fat-shame us, as if we're wrong to want to have many tabs open. Different strokes, folks. There are reasons that bookmarks don't work well. (We may want to be able to retrace our steps in the history for an open tab, which a bookmark would not do.)
And I can confirm that a tab suspended by this tool does retain its history.
Indeed, a quirk I just encountered was that I found (perhaps after the browser restart) that I could not unsuspend the tab by clicking it, like it should (and had before, in testing before the browser restart). But I could just hit the back button and the "previous" page before the "suspended" screen was the page that had been suspended, and all the pages before it in the history of that tab were indeed still there.
And some minutes later I could again use the feature to click a page to unsuspend it.
Time will tell how things go, but again so far, so good.