Static pressure, low and high side pressure at idle and at about 2500 RPM's would be helpful in determining if there is a problem. You say it gets as cold as it ever did after 10 or 15 minutes. With the temperature being as hot as it has been here lately and my Caddy shut up, it takes a long time for it to completely cool off. I keep a thermometer in my center duct and just the other day I got in to go store and the thermometer said 146 F. Outside temperature was 108 F so I rolled the windows down because I knew it wouldn't cool off in just 5 blocks. It takes a little bit of time to displace all that heat before you start feeling cool. After that being said, if you think you still have a problem with your AC, go here
http://acsource.net/acforum/ , these folks are very helpful when it comes to AC.