Can I use my new (2012) 27" iMac as a monitor for my Dell E5510 laptop?

Can I use my new (2012) 27" iMac as a monitor for my Dell E5510 laptop? This is my work laptop and i'd like to save desk space by not having to have a secondary monitor for it. The laptop uses a docking station with DVI and VGA outputs only. I can't seem to find a clear answer on this issue. Some say it's possible (including a Apple store employee) and some say it isn't, without using AirDisplay (which i've read is slow and unreliable). Can anyone attest to whether they have successfully done this?

Thanks!