I am not that impressed with United clubs in general and have been to the following.

Here are mine in order

1) IAH Terminal C - best club I have been to
2) SFO - Terminal 3 - Pretty good drink service and quiet
3) ORD - Dont remember which terminal but it was quite large and had ok snacks
4) IAD- Decent club with similar amenities
5) EWR- brownies were good thats it...
6) DCA - nothing great about this one... except the view