I've been using a 20gal sump matten filter for my 180gal display tank. Tom mentioned one of the reasons I like this setup is that I can hide it out of sight. The other reason I like it is the sump allows me to hide everything else out of sight.

Like any filter the matten filter needs regular maintenance. Mine becomes clogged and needs a good rinsing at about every 3 to 4 months. Because mine is located in the hidden sump which doesn't get direct light I don't have a problem with algae buildup on it.

Although the articles about it speak about the flow rate and more area improving the bio-filter capacity because if in my opinion you either have enough or you don't, I haven't really noticed any difference. If you didn't have enough, you would have ammonia and nitrite spikes, and if you have more than you need it makes no difference whether its a little more or a lot more cause it still gets the job done. Either way you are only going to be able to grow a bacteria colony as large as there is waste for it to feed on.

The low flow rate does however have many other benifits that make it useful in a variety of setups, such as in fry tanks where your feeding live baby brine shrimp. It's fry safe, and doesn't filter all the food out of the water before it can be eaten.
It is much less turbulent for fish and plants, and less CO2 is lost to water movement, depending on setup.

In other setups more current can be a good thing. What matters most is what you are trying to do with your setup and whats works best for that particular setup.