The IDE support is pretty good, I don't have problems with it. Ask the Clojure people how THEIR IDE support is ... sbt is a great build tool, better than ant or maven, pretty much the best I am aware of for any relevant language. The compilation speed is good enough for me, maybe you should upgrade your hardware. If you have compatibiliy problems, don't move to the new version. Wait until you have your issues fixed. You don't need to upgrade your Scala version immediately just because there is a new one.
As to Paul Philips leaving, what was he responsible for, and what were the "bad terms"?
I have a really great feeling overall about the future of Scala. This feeling is based on my 20 years programming experience with all sorts of languages, and Scala is the best one out there right now. The IDE support and tooling is far greater than for any other language that comes close to Scala. (When you code in Java, even the greatest tooling in the world will not help your productivity).
I've done my share of Clojure programming, and none of the tools you mention are usable in a serious setting. The only stuff I could use (and that was damn hard to set up in the first place, and is "deprecated" for a year now) was an Emacs based solution.
I have a really great feeling overall about the future of Scala. This feeling is based on my 20 years programming experience with all sorts of languages, and Scala is the best one out there right now. The IDE support and tooling is far greater than for any other language that comes close to Scala. (When you code in Java, even the greatest tooling in the world will not help your productivity).