Used the filter today for a Lake Walk pale ale, I ended up using 4.5 oz of hops (2.5 @ 60 and 2.0 @ 5). I liked the size, at the start of the boil about 3" of the filter was above the wort. I also like that its a couple inches from the bottom of the IC, I was able to use the hanger as a handle to lift the filter and dip it up and down a bit to free up the hops. I could also lift partially out of the IC and stir up the hops a bit with a large spoon. In the beginning of the boil I was able to see some movement and activity inside the filter, this reduced a bit as time went on as the hops coated the filter. I did put the filter in after the hot break to prevent the break from clogging up the filter.
It did clog up when removing from the kettle after flame out. This comes not from the mesh size (mine is 300) but from the hops creating a mat on the mesh. The last 12oz or so drained pretty slowly but as I moved it around a bit a chunk of the matted hops broke away from the mesh then of course the liquid flowed freely from that spot. I don't think a 400 micron would prevent this as the hops will still mat up on the filter some, it would just let more of the smaller particles into the beer.
I could see this reducing the hop utilization but it appears that enough people are still happy with their utilization using one of these filters. Good enough for me, I'm not ultra picky. With this and my new dip tube from Bargain Fittings I was able to get all the wort from the kettle with no problems.