Product review (4 stars): I like them!
So far so good!  We've only ever replaced our cartridges with the manufacturer's, so I was a little nervous about setting ourselves up with off-brand.  But they seem to be doing great!  The orifice IS a different shape, but it doesn't seem to matter.  We don't have any of the air in the lines that some reviews have talked about, and the water tastes great.