The burgers are DELICIOUS, as well as the fries.
Yes, the service can be slow at times but there are limited servers (many of which are new since they hire often) being screamed at by drunk students and alum at all times, so you can't blame them. Typically the staff is very positive and polite despite the high demand crowds.
Also, Joe's is extremely casual and is also a college bar. As long as you come in with the mindset that your food may take longer than you would prefer it to, you will have a great experience with delicious food!