In my experience the 1M context is genuinely too much. The first time I swapped from OAI to DSv4P, I checked and double checked that the harness/etc was working correctly over the course of hours and hours of work thinking that I had set something up wrong because it simply never had to compact! The drop in quality is arguably less than that of what you get from compact to compact on Codex, which is good for what it is or was.
Was also surprised to learn just how much of Codex's window was being burnt on shit I didn't want or use. Sure I can pass this and that flag to eliminate most of it, but for a $200/mo product aimed at professionals, that isn't something anyone should have to janitor (also totally ignoring the bandaid of banked resets they've slapped over their repeated mistakes).
It's wild just how far $20 will get you with Deepseek, even at their new rates. Buyers Remorse is my very least favorite feeling, I felt sick thinking about what the $1200 I had given OAI this year would have gotten me had I only tried sooner.