As explained by Is it Okay to Use an HDTV as a Computer Monitor?, it all comes down to resolution, not screen size:
If the bulk of your computer usage is browsing articles on the internet, reading email, writing, or anything similar, the biggest problem you'll have with the bigger HDTV screen is the lower resolution. Text will look fuzzy and hard to read--especially up close--when compared to most high-resolution monitors. Remember, when it comes to monitors, resolution matters most. A 32-inch HDTV can sport the same resolution as a 27-inch monitor (assuming they're both 1080p), but blown up an additional five inches. This makes everything a little fuzzy and not conducive for reading.
That all said, if the majority of your computer time is enjoying media and reading the occasional website for less than hour, a HDTV+computer setup could be more economical (and also a space saving solution). If you're fortunate to have several monitors, a HDTV could be the centerpiece, as displayed here. Or if you've got a laptop you occasionally like to hook up for some home theater PC action, then again, the HDTV with computer connection can be a pretty fantastic duo. Just make sure your set has the correct ports to make the connection!
>> Is it Okay to Use an HDTV as a Computer Monitor? at Lifehacker.