Similar issue. I am a PC user and am wanting to make the switch to an Imac and Promise Pegasus storage. I need at least a 3m TB cable to put the Pegasus where I need to put it. As far as I can tell longest is currently 2m and while on copper, longest recommended is 3m (but none available) but there is the promise of optical TB cables next year that could be 50m+ in theory.
Apple recently released a 2M 6.5-foot long Thunderbolt cable. I have a 27" Thunderbolt display that sits about four-feet away from my iMac, and just hooked it up. Don't use the Thunderbolt cable that is attached to the display; instead, connect the display to the computer using the 6.5-foot Thunderbolt cable. Works perfectly!
Besides the monitor, do the other things on the display work when connected this way, such as the USB ports and Ethernet port? I would be making heavy use of these if I got the display, but I'm concerned that the attached pig-tail cables are too short. Do you know how long the pigtailed Thunderbolt and Magsafe cables are -- the specs don't say.
Thanks for any advice you might have.