From a IFR flying pilot's point of view, Class E is probably also awful, compared to ATSOCAS with Traffic / Deconfliction service.
Why?
- It does not offer any real additional protection [IFR/IFR separation is nice to have, but only covers a small fraction of traffic]
- But now I have to file flight plans, deal with IFPS etc. just to go IMC. Currently I just ask xxx Radar if there is any traffic to affect and climb on top...
The only advantage would be that I can "stay in the system" in areas where there are currently no [Class A] airways or the current Class A base is higher than I want to fly on the day. And in practice the latter, while requiring a bit of extra negotiation with ATC, is no big deal.