the g11 is pretty good. i dislike it because the macro bank adds too much bulk (i already have a keybaord/mouse/macropad combo taking up all my space). if thats not an issue for you, its a very good keyboard.
i havnt used a g110, so i cant really comment. it looks nice though
i love the x6, of all my gaming perihperals its the one i really never get annoyed with, or wish id bought something else. i like that the keys have slightly less travel than a normal board, so you dont have to push keys quite so hard. as a gamer, that really helps me. i dont have any ghosting issues at all. i play games ALOT, and ive been pwning in MW2 recently and can easily diagonal strife while sprinting and reloading. no issues at all.
for me, the sidewinder x6 is about perfect. plenty of macroable keys, but unobtrusive. the moveable macro pad always stays on the right for me. but being able to detach it so my whole board fits in my backpack is a real time saver for LANs.
backlighting is good, its nice to type on. the macro software is easy as hell to use. i just love it.
i like my g13, but sometimes feel i didnt need to spend the money on it. the x8 is awesome, but its big. and when my hands get sweaty i often have ahard time gripping it properly.
the x6 though, i love.