It all depends on how you choose to use parallax. If you employ a buch of blurs and other effects that effect the page performance, it only makes since to rethink your approach. Just like when Flash was big. Everyone wanted everything to be Flash. Some did it very well while others who thought it was cool failed hard in the UX department. Parallax when when used sparingly can be an elegant visual effect. However, over do it and your project will suffer.
So if you are having performance issues with scrolling you may want to look at how you have implemented your code and look for a more efficient method. You may need to scale it back. Ask yourself if what you have in place even makes sense. Determine if it's necessary and evaluate it's value from a UX perspective.