That is a fantastic price on a fantastic mouse. I got mine 4 years ago this July and I'm still lovin' it. I've never owned a better mouse for gaming.
And yes, rebates are a hassle, but in this case, I think the value would be worth it. Yes, Logitech has manufactured newer mice (mouses?) since the MX518, and no, I haven't had a chance to play with them, but why upgrade when there's no need? And for those shopping for a new gaming mouse, $10 for a MX518 is a terrific value.
<3 Logitech. Left hand: trackball (Marble Mouse), right hand: gaming mouse (MX518), living room: cushy keyboard and mouse (Wireless Wave Combo MK550).