I wear armwarmers and kneewarmers starting in the lower 60s. They get me through the 50s. I start thinking about tights and longsleeve tops around then, usually with the armwarmers. I have little stick-figure arms that get cold easily.
It's nice to have options and combinations. I have cold weather wear that gets me down to 0°F.
Edit: When shopping for tights, look at "windfront" tights. I find I like that kind better. Less breeze blowing through them, but still open enough in the back to keep from getting sweaty.