I gave Benny's an overall of 2, which I'll try to justify by going through the other rubric parameters first.
Food: I've only had their coffee, their smoothies, and a veggie samosa. While the samosa was hardly authentic, it was still delicious--think Greek phyllo dough wrapped around spicy chickpeas, onion, and carrots. Yum. The smoothie was fine, just berries and banana, plus ice. A bit pricey for the portion. Their drip coffee is rich and hot, and they make a killer mocha, perfect proportions of coffee and chocolate, and very creamy.
Service: Friendly. When I was last there, the barista made a mistake, giving me an americano instead of a mocha. She instantly realized what she'd done, told me, and made me a new one immediately. Yeah, it wasn't right the first time, but extra points for acknowledging your goof and fixing it!
Ambiance: This is where it really falls down. They need to walk around the tables more frequently, because a lot of their customers fail to bus their own tables or clean up their spills. They also need to know how to draw the line between coffee drinking and studying--if you go in there any given weeknight, 90-100% of the tables will be occupied by people staring unblinkingly into their laptops. This is especially irksome when it is one person occupying a table that can accomodate four. I'm not a big fan of Calhoun's "no books on tables" policy, but something needs to be done so that customers can actually enjoy their drinks.
If Benny's would reign in the studyfest and clean up the tables, I'd give them a 3 for ambience and a 4 overall.