When I used it before Christmas (free trial), it very visibly paused for a bit every so often, telling me that it was compressing/summarising its too-full context window.
I forget the exact phrasing, but it was impossible to miss unless you'd put everything in the equivalent of a Ralph loop and gone AFK or put the terminal in the background for extended periods.
However I run like 3x concurrent sessions that do multiple compacts throughout, for like 8hrs/day, and I go through a 20x subscription in about 1/2 week. So I'm extremely skeptical of these negative claims.
Edit: However I stay on top of my prompting efficiency, maybe doing some incredibly wasteful task is... wasteful?
