Not sure if you are serious of just fucking around. @Wildest
Anywho, I have used Cydia for a long ass time now, my uncle introduced it to me like 4 years ago when I had my first iPod. I now jailbreak my own iPhone and iPod. I am still using ios 9.0.2 and I have a lot of fun. I can download apps free, use MovieBox, download any video or song from Youtube using Youtube ++. I really enjoy it and no, it doesn't slow down your device unless you install a lot of tweaks.