Assuming the HDTV looks good for movies and TV, then it should also look fine as a monitor. Text on a HDTV will not look as sharp as text on a LCD monitor because the pixels are arranged more for shapes than text. You will need to play around with the sharpness to find something that's good for you.
I haven't had a plasma display either, but since it's emissive (LCD is transmissive), it can offer much better static contrast ratio, and response time is a non-issue for plasma displays. However, they tend to be 42 inches or larger, which is impractical for most desk setups - you'll probably want to be able to situate it 3-5 feet away. Also, many of them are listed as 600Hz, but that's only internal - they still only take 60Hz signals, so they probably interpolate the extra frames, adding to the input lag.
A 600Hz Plasma TV pulses 10 times each Hz cycle (or frame); so 60Hz x 10 pulses per Hz = 600Hz. This is known as Sub Field Drive. Think of pulses as a form of refreshing or updating the pixels. The more pulses per second the less ghosting and image blur there should be.
It has nothing to do with video frame interpolation.