The Store 24 in Harvard Square should be called Store 23 instead, because it closes for an hour around 3am every day for cleaning, although the people working there really just stand outside and smoke pot. They don't carry Slurpees or beer, which is really what makes convenience stores worthwhile.
On another note, the Sto' Two-Fo' in Harvard Square has since closed, and has been replaced by a C'est Bon convenience store. Now, the help is rude and doesn't speak English, instead of just rude. Plus, everything is more expensive. I'm actually quite glad I don't live there anymore.
There are still Store 24s all over the place, though, still catering to stoned teenagers and college students (do the math: Little Debbie Nutty Bars are 25 cents for a pack of 2. For only $10, you can have 80 Nutty Bars! No one has the munchies bad enough to eat 80 Nutty Bars. Trust me. This is why Store 24 rules).