Definitely, no phosphate would be bad. Really it's tough to get really low, even with all the filtration you can come up with.
For example, another good article on phosphate
http://reefkeeping.com/issues/2006-09/rhf/index.php
From it, reefs average around .005 ppm of phosphate.
Also:
"Flake fish food is typically about 1% phosphorus (3% phosphate equivalent) by weight (and many products have such phosphorus data on their labels). Consequently, if five grams of flake food is added to a 100-gallon aquarium, there is the potential for the inorganic orthophosphate level to be raised by 0.4 ppm in that SINGLE FEEDING! "
Granted, other foods are not necessarily as high in PO4, but only differ be relatively small amounts really, so, still will raise phosphate significantly. In the ocean, generally corals derive most of their nutrients from various food sources, which tend to be scarce in our systems. The .005ppm is not where they are getting the bulk of their PO4 from. If you feed, a reasonable amount, the risk of reducing phosphate to ocean levels isn't an issue though anyways. So, in our systems, it may very well be more likely that corals in a low nutrient system, still aren't getting enough phosphate, even though phosphate levels are higher than in the ocean.
I think that's why a lot of people will say that the point of extra filtration is to be able to feed more. You don't need/want to lower nutrients too much. However, really though, when filtration gets efficient enough, it becomes not just that you can feed more, but really that you need to feed more.
Personally, I've been using GFO for a long time, more than 7 years I'd say, and combined with various carbon dosing off and on for almost as long and have not had significant STN/RTN issues. Generally even SPS corals will get thicker, denser tissue after being in my system for a while, even though phosphorous averages around 1-3ppb (approx .003-.009ppm phosphate) on a Hanna ULR phosphorous checker. I feed a wide variety of food including cyclop eeze 5-7 times per day though. While PO4 is low, there is still a constant input and a number of potentially available food sources.
A lot of people who add carbon dosing and/or GFO and do not have significant nutrient inputs, certainly do report problems though.