I've decided my install of Lion is hopelessly botched. Spotlight doesn't work, kernel panics, etc etc etc. Want to reinstall. If I reinstall Lion from the recovery USB key I have, it will retain all my data correct? ie; not format the drive and reinstall.
No, Lion does not perform a format of the drive, it simply replaces the contents of your system with a default installation.
Once you install Lion again, all your files, your user information, account settings, installed programs, etc. will still be there.
Moreover, it does not leave a copy of your old system, like Snow Leopard before it.