Just switched back to dailies from A7.2 because a daily build plus material editor gave me over 5 minute work breaks randomly when clicking on a slot to bring up the Material/Map browser. I tried out RC2 and 3, and everything ran as smoothly as ever including both slate and compact Material Editor! But just now I had the problem occur again when I tried to nest my Blend Corona material into a CoronaRaySwitchMTL. Task manager shows Max is using 8% of my cpu power, sharp. EDIT: took 20 minutes but now Max is usable again.
Ondra, since last night was absolutely flawless with no crashes and not one of these Material Editor freezes, did you manage to find out whats causing this behavior for some of us or has it gotten better without you actively hunting for it? it's still there, but seems to show itself more rarely.
If it helps in finding out a cause for it, I recently found a way round it was to create materials in Slate Editor, and never load up a map through the Corona Material itself, but to right-click on empty space somewhere load up whatever map I needed as its own thing and THEN connect it to whatever channel I was planning on using it for. I still migrated back to A7.2 in the end because every now and then I'd forgot this workaround and go load the Map Browser through Corona Material.
I'm ready to shove money your way right now because Corona is amazing but this said problem is extremely time consuming and I'd love it if I never had to see it again.