Ever since I installed v.15, Premiere takes 15 to 20 minutes to be usable as it freezes up until it's finished writing some kind of data to the raid drive. I actually get the spinning beach ball as it writes, then finally finishes and I can work.
I've tried a complete Prefs/Cache reset on start. No luck.
One thing I noticed is that where the problem is, is it's taking a long time to connect to the media. It will stick on one file and I can see the raid working on it, then it frees up and starts connecting more assets.