I have 0 game lag with my logitech lx710 and it's quite, quite old by keyboard standards now. There's a substantial myth surrounding 'game lag' with wireless keyboards that's pretty unfounded, generally. I would imagine a bluetooth 2.4 ghz connection may be even more stable than the Logitech Unifying Receiver thing, which is why I might just give the morphling kb-87 a try:
http://www.aliexpress.com/item/Morphling-Backlit-Wire-Wirless-Mechanical-Keyboard-Red-Switch-Brand-New-in-BOX-Fast-Free-shipping/934354240.html
I figure that if it does skip occasionally wireless I can still connect it via the micro-usb and use it that way for intensive stuff. At least I have the option of being wired/wireless with this model and the backlight is a nice bonus. No real reviews about it floating around so I'll be taking a chance either way ;|. One good piece of news is it's based directly off the plum 86 hardware (just with leds and a backplate added, it would seem) and that keyboard has been pretty well received. In fact, I almost opted for a plum 86 instead but I figured an extra 20 for led's installed isn't a bad deal.