I have em...
This is my first an only pair of monitors at home. I have mixed on NS10s, larger KRKs, Genelecs, and Adam ribbons. The thing I've noticed: the room is far more important that the speakers. Also, having a good 1/3 octave EQ in front of any monitors and a RTA to show you your boosts and cuts is pretty critical. That being said, the mid-lows can be a bit hot. Tame 'em with your EQ. If you don't have the hardware, use your DAW's parametric EQ to do it.
Honestly I don't trust any first mix anyway. My room (and most of the rooms I get to use) is far from ideal. These monitors are intended to be cost effective, not perfectly true. But here's the deal, spend your money wisely. Treating you listening position is far more important than the flatness of your monitors.
It probably is true that you can get "better" monitors for the price, but chances are if you're looking to spend less than $500 a speaker, you're new to this and it won't matter anyway.
Treat your space. Get some monitors. Listen to music (from CDs! not mp3s) that you know very well. Use a RTA and some sweeps. After a while you'll learn you speakers.
Would I rather have something else? Sure. Would it matter in my room? I doubt it. As far as monitors are concerned get what you can afford. If this is what you can afford you'll be ok!