Cordless or corded isn't a big deal to me. My mouse sits a good 2" in front of my tower and an inch to the right of my keyboard. I've used several MS and logitech mice, both corded and cordless, and never had a preference, it just doesn't matter for me.
The one major concern I have is the mapability of the buttons on the MX1000. I changed nearly every key on the MX500 series to my liking, and noticed that the MX1000 changed the left side buttons. I map the left side (thumb) buttons to show/hide desktop (front) and double click (back) but if I'm not mistaken, the MX1000 has 3 buttons there, and I guess removed one of the top ones? I use the wheel in front of the scroll wheel for 'backspace' (back in a browser, and in most programs) rather than using the side ones for back/forward.
I'm going to get a new mouse fairly soon for my second comp, so I could move my MX500 to it, and add the MX1000 to my main comp, or save some money and go either MX500 or 510 on either comp. I like the look and love the 4-way scroll of the wheel on the MX1000, but I'm still not sure.