First -- most AMP connectors are first rate. Much better than Molex in my opinion.
Plus --> Available in a wide variety of sizes all the way up to 36 pin.
Plus --> Somewhat affordable (but considerably higher than the old Molex plugs were).
Plus --> Box contacts can't be beat for reliability.
Minus --> even with the low pressure contacts (part number 86016-3), about 27 box contacts can be a real bugger to push onto the header. I have had some of these contacts actually break off the locking tang and push back out through the back of the connector. But majority of time - they work fine.
Minus --> Good crimps with these pretty much require using the AMP Certi-crimp crimpers...VERY expensive. Part number 91516-1. Can often find used ones on ebay.
For those that want AMP part numbers:
28 pin plug = 5-87499-4
contact = 86016-3 (not 571-860163 as above)
keying plug = 86286-1
Don't try the intermediate or high pressure contacts with high pin count connectors. Those require a sledge hammer to get them installed!
Oh, and one last minus for AMP connectors in general. Who created their part numbering scheme?!?! Their part marking has no rhyme or reason to it. At least with Molex and others, you can guess at part numbers based on product family and pin count.