I have been ordering here for a while as well - about 10 years and it still remains my favorite American style Chinese place for take-out (or eat in). I have experienced some of what you claim but maybe not to the degree you have. Their prices have gone up and their service has gone down, in my opinion. The people answering the phones are not the nicest and at one time, I thought they were pleasant. Delivery times have increased to about an hour on average - it used to be about 30 minutes. As for the delivery guy, I really can care less if he gets mad about the tip. I always include one - usually $3 or so and there is a delivery charge on top of that.
These problems have not entirely dissuaded me from ordering from there but my frequency has dropped in the past couple of years.
For people not familiar with Papajin; they do have better than average American style Chinese food. Their ingredients seem fresh and of a higher quality than most. Their dishes seem less oily and salty than many others I've had as well. They claim no MSG and I guess that's a good thing. When you order lemon chicken, you'll get large slices of white meat chicken, when you order a shrimp stir fry, you'll get a generous portion of large shrimp (if these are things you are after). The prices may be higher than some but I feel the quality is still much better than most.