Whether it's real or illusory, I feel like they turned the bitrate down significantly since launch. I'm not getting as many smart electrons per question as I used to.
On the API: My prompts are getting 'harder' and expecting more. My old prompts still work just fine still.
On the website: Copy pasting the same old prompts still work... but the 'flavor' of the text that pops out definitely feels worse.
I haven't seen any actual data showing a degredation.