Userland code - games and emulators in particular - are largely unaffected by this patch, on the order of about a 1-2% performance difference, if any.
This patch is extremely important to install unless you're comfortable with the thought of any site with a potentially-malicious ad being able to easily and quickly grab all of your passwords.
I really, really hate that all of these articles just started scremaing about "30% performance loss!!" without clarifying what sorts of workloads would be affected. I wish I could slap the piss out of the article authors, and I wish I could slap the piss out of the people breathlessly running to e.g. emulation forums to scream about the impending performance loss that isn't actually going to happen for userland-bound code.