Since upgrading to 4.0.1 build 4058, IEA has been stuck on, regardless of what I've set under options. Is there any way to remove this?

Sorry, what do you mean by that? Please submit more details about how it's happenning, and contact me by email if possible.
Thanks.

It's quite simple, the Instant Error Analysis that gives the wavey red lines under syntax errors is always on, always highlighting errors. I've turned it off in Tools > Settings > Code Insight but regardless, it stays on. The tick box correctly responses (ie. it remains unticked even after closing the settings and restarted PHPed), but I get the wavey lines regardless.

good news. It's fixed in build 4059.