Spent a whole evening to confirm this..
Using the latest XCode 7/iOS9/WatchOS2 Beta 4.
Watch Apps written in Swift pretty much doesn't work at all. They either take an absurd amount of time to start up, requiring the workaround mentioned in the Release notes. Or once they do start up, they do not perform the expected functionalities reliably.
On the other hand, the same code written in ObjC works. This is very frustrating. Wondering if anyone is seeing this as well.