...and give yourself at least a week to get into it. In many ways it's like learning a new program.
There was a learning curve with X1, but ultimately I was able to get projects done faster. If you had 8.5-specific workflows they may or may not be possible with X-series software, or there may be improvements, like comping (which I think most would agree really rocks, once you figure it out).
The Melodyne thing is huge, as is VST3 support. Waiting to come on board until X3 was probably a good move as it's a much more mature program compared to X1.