How you finding it? I was playing with my newly acquired SB900 yesterday, and those flimsy gels are a pain.
I have not had a chance to use it extensively for portraiture, but after a few quick practice shots of my sister, I think it will earn a place in my bag. My unit was purchased as previously owned, though unused, for $70.00 so at that price point I was willing to experiment a bit.
I would actually recommend it, as it is a much better alternative to the flimsy gels you mentioned and awkward DIY solutions out there; the magnets keep grid and gels in place with a professional, polished look, if aesthetics are as important as basic functionality, to you.