I've eaten solo at the bar hundreds of times.. I've eaten solo at a table hundreds of times.. There are two problems eating at the bar:
1. the counter is a bit high to do "real" eating (e.g. knife/fork) like steak. Fine for finger foods like burgers and fries.
2. I spend a lot more money at the bar. Bartender is a lot more attentive to my empty drink than a waiter/waitress covering multiple tables..