Paisano's in Rockville
Paisano's in Rockville is barely Italian. I spent two years working in the office building across the street (now under renovation), and we ate a lot of meals there when we were too lazy to visit the good restaurants. They serve some basic Italian standards, but I was thoroughly unimpressed by any of them. Let's put it this way... After some experimentation, I settled on a standard order of a chicken sandwich, steak sub, or buffalo wings. Note the lack of Italian food in the acceptable dish choices. :-)
I agree with the other poster - Il Pizzico is a MUCH better choice. It's in a dingy little strip mall next to the Jiffy Lube and doesn't look terribly impressive. Inside, you'll find inexpensive Italian dishes prepared with care. Nothing innovative, but everything we've tried has been satisfying and the service is friendly. And yes, it can be a bit of a wait to get in on weekend evenings (and sometimes weekday evenings).
There's also Cafe Vignola on North Washington Street (in the shopping center with Magruders). I've never had a sit-down meal there (heard it's pretty good, though), but occasionally swing by for a mozzarella (made in-house) and prosciutto sandwich. Yummy.
I can't comment on Paisano's, but I do enjoy Il Pizzico. It's a small place on Rt. 355 (not sure whether it's Rockville Pike or So. Frederick Ave. at that point) north of Gude Dr. in an unlikely-looking little strip center on the east side of the road.
Nicely done pastas and veal and not too expensive for the food, in my experience. It's not the sort of place in which you get an oversauced, gargantuan portion of spaghetti and meatballs (which is a big plus, imho). My favorites are the pastas that are sauced with a "rosy" sauce or a cream sauce.
Since it's small and popular, you might want to go during the week to keep the wait for a table to a minimum.