Yosemite, along with IOS 8, has had its fair share of problems. This has proven to be one problematic OS release for Apple and their customers. How far we are from a final release point to the public is difficult to judge but would likely depend on how able Apple is to quash some very annoying bugs.
At the very beginning of the release of the OS one of the most trying aspects of the system was its inability to maintain a solid WIFI connection. Additionally, there were many bugs that had to be dealt with to maintain stability.
Under the Hood
In an article named OS X 10.10.4 Beta 6 Released for Testing from the OS X Daily, they point out that Apple is doing a significant under the hood change by returning to mDNSResponder from the problematic discoveryd networking daemon. The hope is, despite multiple OSX releases, this will stabilize the networking component of Yosemite.
To say that this has been a frustrating OS due to the number of significant issues confronted by Apple engineering is an understatement. For Apple users this has been particularly troublesome as the company is many releases into Yosemite without a solid Operating System. Apple users are not accustomed to such instability in their OSs making this one of the most problematic updates they have gone though.