HDTV as a monitor works fine (at least if the tv is true 1080p native). I'm using one now (though I plan to get a higher resolution monitor in a few months), and I think there are others here already using hdtvs as monitors.
Advantages of using an HDTV:
- extra inputs like component and composite, which are useful if you have old video game consoles to connect
- if you're lucky, good speakers so you can save deskspace and have one less power plug to deal with
Disadvantages of using an HDTV:
- no DVI or DisplayPort (screens with one or both of these are generally marketed as monitors rather than TVs, even if they have extra inputs and a TV tuner)
- often tricky to get native resolution working right with HDMI connection (requires tweaking the video card overscan/underscan setttings and the TV's scaling settings)
Those are the only general advantages and disadvantages I can think of, but if you can provide the manufacturer name and model number for the HDTV you plan to use, I might be able to find others that are specific to the model.