Yes, you can indeed in most cases have cold air quick and easy with one of these kits. There is an old adage that comes to mind though, that is: "If it looks too good to be true, it probably is."

Evacuating the system is NOT merely a means for the shop to charge you more money. It IS a means of removing the dreaded moisture from the system. The moisture H2O(part hydrogen) mixes with chloride in the refrigerant to make an acid. This acid will eventually eat a hole from the inside out somewhere in your system. For a long term fix, you really need to evacuate the system prior to charging.

This also reminds me of a slogan of the old Fram oil filter commercial, that is: "pay me now, or pay me later."

Best of luck,