OK, just bought a honda civic dx, excellent shape and condition. I've noticed it shifts a little lazy... does that have anything to do with the shift lock release on the shifter? What exactly is the shift lock release?

Shifting quality and performance will improve a lot, if you change the transmission fluid and filter. I found dramatically improved performance from using full synthetic ATF; e.g. Mobil 1 Synthetic Multi-Vehicle ATF and Amsoil Synthetic Universal ATF. The shift lock release doesn't affect shifting quality.