I think that the reason that many consider them good is that they are decent built and a new power supply usually tests out very well, even under full load. they also work just fine for many people (though plenty have also had them prematurely die) The problem is that antec seems to think that power supply's must be as silent as possible. the fans run to slow and do not speed up till the power supply gets way to hot. Regardless of your computers case temperature, the power supply's own heat kills the caps. I have to wonder if the reason that none of mine have died, is I usually run positive case pleasure. By that I mean that more fans are blowing in than out. I do it so that the extra air gets out through cracks (like around pci slots, optical drives), so that they get a little air flow, but I imagine that some goes through the power supply to, and maybe that little bit of extra cooling is enough.
I did find out for sure that they have changed oem's on at least some of the new power supplies. they have been using channel well, but at least some of the new ones are confirmed to have been built by seasonic (I think it is the trio and neo that have been confirmed to be so). Keep in mind that means, they will have similar design to seasonic, but will not nesasarilly have the same quality of components the actual seasonic branded ones have. I would suspect that they are decent quality, but I wonder if they will stick to this, they must be silent no matter how hot they get approach. If they do, it could kill the new ones too.
On a side note, from what I have been told, if you feel like modding it, you can bridge the temp sensor and they will run the fans faster.
Just a disclaimer, this is what I have been led to believe from other forums, though I personally only own 4 antec power supplies and have installed a handfull for others.