I had my old rear projection done as part of the purchase price.My new dlp was done in house.The latest Toshiba software was uploaded and then a calibration was done.It took about two hours,and a report of before and after temp settings and user settings for each input were e-mailed to me.Black is now black,with the spectrum of greys up to white.The black level before cal. was a dark grey.Flesh tones and colours are much more defined.I personally wouldn't by another big screen tv without a calibration,but most people don't see the need until they've seen the difference on a before and after set.
As a side note it cost me $300.A dark room is preferable.The price may vary as to the make and type,i don't know,but use a certified ISF tech with the latest gear for the newer sets.