I was playing the game for little less than a week before I really noticed it. It had been there from the beginning, of course, but I was too busy drooling over the different types of bushes blowing in the breeze to notice it with complete consciousness. That's the way "visuals" usually work.
These reddit.com tweaks mentioned above are really at your own risk. Generally, assigning "high priority" to programs is not a great idea -- they can overrun specific Windows processes and create errors with kernel.exe. I doubt anyone will fry their system nowadays, but it can still lead to system instability and memory errors.
Rather than raising priority, try to kill intensive processes running in the background. Sometimes, when I've been very desperate to solve something, I would manually shut down explorer.exe. This kills 90% of windows processor and memory usage safely. You'll need to write a batch file to start the game manually through Task Manager, then restart explorer.exe through Task Manager when you're done. It may seem scary, but it's a heck of a lot safer than mucking around with program priorities and basically accomplishes the same thing.