So after today's 1.32 patch update riding in a minecart is extremely slow. In fact I can run faster than riding in one. Nearly had a Creeper catch up to me and blow me up!
Other things seems to be laggy/losing Framerates. Opening doors, gates, eating, xp orbs lingering, mob drop items take too long to pick up......
I've uploaded a Game save where you can check for yourselves. When you load the save, you'll be standing beside a Minecart ready to take you for a ride. You'll see what I mean by 'really slow' as soon as you push yourself off.
Game save @