I've been wrestling with this issue for several weeks, and put off ordering a new MacPro because of it.
Based on some of the other threads I've read on this topic, I am strongly considering getting a Dell 24" display instead of holding out for a new ACD built for use with Apple's towers.
When I went to the Apple Store this past weekend to measure the actual length of the cable on the 24" (and verified that it is far too short for me to keep a MacPro tower on the floor under my desk) the salesperson I spoke with immediately pointed me to Monoprice.com, which apparently plans to sell an extension cable for the display. (This would only cover the "video" part of the cable. You'd be s.o.l. on the built-in magsafe adaptor, and you'd have to use a basic USB extension cable to run the USB port). So at least the salespeople are already aware of the issue.
Instead of messing around with all that crap, I'm tempted to switch to the Dell display, which would meet my needs, and also provide more flexibility for different types of inputs. Yeah, its not as pretty, but it is cheaper and would get the job done.
Most people would call me an Apple fanboy, and I've certainly encouraged plenty of other people to make the switch. But their decision to roll out pricey new towers without compatible displays is baffling to me. Is it obliviousness or arrogance? Or do they really just want us to get our displays elsewhere?
I'm waiting until WWDC to make a final purchasing decision though.