I agree with you Rob... Next to the economizer gaskets, the biggest source of leaks is (ironically) the place where the non-condensables are supposed to be removed.
The new flange kits are definitely the fix for those things. On smaller ones with 4 bolts, I've had some success drilling and tapping the additional 4 holes. Even on the 8 bolt and 12 flanges, if you are meticulous with your installation and pay attention to the details, they're not problems anymore.
The purge is the lowest common denominator. It's a whole lot cheaper and easier to fix than pressurizing the chiller and leak testing. There's a short list of things that I always check on every one before I go and pressurize the machine for a leak test.
I agree, Rob. The Purge is key to the chiller. I would always do a quick run test and inspection of it on all service calls I went on, even if the call was not purge or head pressure related. Sometimes I would find extra work. More than once I found "Max pump-out rate exceeded" that was a month or more old and still active (not ever reset).