On the current setup used to visit this place, the re-done MX500 rules my world but on other machines in the house, down the hallway in bedrooms, office, storeroom and garage it's Mionix Naos 7000, SteelSeries Rival, Roccat Kone Optical, Roccat XTD, Logitech mx1100, MX Revolution, G500S, G400S, G9x (wifey loves it), IE 3.0 and a Microsoft Sidewinder mouse (no kidding).
All of these mice get used but the MX500 gets the most love at this particular moment in time. IT would seem I'm a Logitech fanatic yet I don't feel like barracking for them in any way on this forum or on any other.