Replace monitor with an HDTV ?

I need a new monitor for my home office. It will be used extensively --- office work and web browsing in the day, then photo editing, games, and movies in the evening. I was about the pull the trigger on a Dell 2709w ($625 shipped). But then I thought, why not use an HDTV as my computer monitor?

The Samsung LN40A550 is selling for $900 shipped. I can mount it on the wall facing my desk, approx 1.5 meters away. Are there drawbacks to using an HDTV as a monitor?

The 1080 vertical resolution seems good enough to me. But my main worries include: software compatibility, display quality, eye strain, and the TV's durability. I don't know if TV sets are designed to carry the same workload as computer monitors. Most of my previous monitors lasted 5+ years of heavy use without problems.