I am sorry to say, but it not user friendly at all.
Keeping track of so many addresses can be a real pain especially if I am a successful shop with 10 - 100 transaction a day.
It seems that bitcoin is not suitable for large scale # of transactions.
Large scale implies you are serious about your business. This implies proper effort related to accounting, supply chain management, legal, IT, and - yes - Bitcoin infrastructure. What you are complaining about is trivial, to say the least. Get serious or get out.