As someone who spent quite a bit of time in Patong I can say that all of what you said above is correct. As with many other beach areas in Thailand, you will never be left alone. You are constantly harassed to be spending money even when you are currently in the process of doing so. The people entering restaurants to try to sell you things while you are trying to eat is super-annoying and I don't know why the restaurants themselves do not prevent this.
The beach there, especially if you are on one of the mountains overlooking it, is spectacularly beautiful... However, being on it is an exercise in patience because once again you will not get a moment's peace because of all the touts that are constantly pestering you.
I think Phuket's beach areas are basically ruined because of this, especially Patong. If you plan on staying on the island for a while get a bike down to Nai Harn. It is my favorite beach in the world and there are far fewer people there and therefore, less harassment.