I hate post offices too, they are always shabby, contain people who cough a lot and when you get to the counter you find that they dont offer that service here!
Co-Ops on the other hand are even more annoying. Their own brand food isnt that good but they do sell good brands too so its not that bad, apart from the prices. I usually find the staff surly and slow, spending more time chatting than scanning. They also seem completely oblivious as to the purpose of bottle seals and wont let me have more than 2 carrier bags regardless of the amount of shopping i want. They insist on placing obstacles in the aisles and in the entrance so you cant get past the danish pastries, the ceiling is usually stained from the air conditioning and they have poor stock levels.
On the plus side, they are often conveniently located but closed in the morning so you cant get some milk and a sandwich for work.
Other than that, and the checkout operators friends sitting on the bag packing area, they are an excellent addition to the local economy. Fortunately, Tesco are on their way and I can see why they are so successful.