1998 Jeep Cherokee Repair failed

We bought this Jeep a couple of years ago, and the a/c has never worked (I had it recharged once and it only held it for a week or so). I have no idea how long the a/c has not worked on this vehicle.

We decided to have the a/c system repaired. I took it to the local Jeep dealer. They replaced the compressor, the "acc" (not sure what that is, cost about $130) and a tube and a hose, to the tune of $1,563.49. But, when I picked it up, it was barely even blowing cool air, let alone cold. I took it back the next day, they agreed that it wasnt' right, kept it another 2 days. They promised that there were no other leaks and they recharged it again and told me it was blowing "freezing". I picked it up yesterday, and it was better, but still not really cold- definitely not freezing. I drove it today and with the hot sun coming in the window, I could barely even tell there was A/C on even though I had it blowing full steam. I just don't think this can be right. I would expect that an A/C system on a vehicle of that size could freeze the front seat passengers! (I have an 11-year old Acura that blows twice or even 3x as cold as the Jeep A/C!) Since I didn't own the Jeep when it was new I have no idea what the capacity should be. Also, if there are no leaks in the system, and it is fully charged up, what could possibly be wrong with it? I'm going to take it back again, since the dealer MUST make this right, but I'd like some advice on what COULD be the problem. Those guys could possibly just hope I'll go away and leave them alone. But for the price I paid, I feel like I should have a system that works and works well!
Any advice?
Thanks!