If you put it with a weak "3 ton" blower, it could run shy of full airflow. If you have a stronger blower, it is fine, may even have to slow it down depending upon the duct system.
How many people would put a new compressor in something 10+ years old even if it were in warranty? What will we have for refrigerants and technology in that time? With people being so mobile, how many are in the same home 10 years from now?