Your SCT X-Cal will take care of the speedo prob. As far as shifting, I have had no problems. It's a tad jerky when I get on it, but nothing major. Aside from the headaches from an improper install, they are pretty awesome. I could have lived without them, but if someone pulls up to you at a light, these will certainly help change their mind about the next time.
Just make sure you have a good gear guy doing the install or you will be sorry.