I love Fran's.
My favorite is their Irish Coffee. They make it strong and for only $6. My last one was so strong that my waiter asked me if I was going to be driving after because he wanted to warn me that he had made it a little heavy handed, hah!
The food is a little more expensive than you would expect from a diner ($14 burgers, $10 salads) but the food is really tasty and the portions are so big I usually have to take mine home. Since it is a little pricey, I usually stick with the Irish Coffee and an starter. The starters come so large that you could eat it as a meal no problem. I've never had a meal from Fran's I didn't enjoy.
The decor is pretty cool, and it's in a great area AND it's 24 hour.