In the office, I use a Dell U2711. I bought it because I needed dual inputs... one for my Lenovo X201 and a second for my Apple 11" MacBook Air.
At home, I use Apple's Thuderbolt Display. As stated above, it uses the same panel as the Dell... but it has a glossy screen.
Personally, I like the ATD better than the Dell. In my case, I can control the light to avoid a window reflecting off of the screen. If you cannot control your room lighting, you might prefer the Dell.
I find the anti-glare on the Dell to give the monitor a softer look. Text in particular does not appear to be as crisp as the Apple.