I've read all of the same things as Nicole is mentioning above - that ANY television at all for under 2s is a huge no no, and for all of the reasons above.
That said, my DS has been watching TV since about 15/16 months, regularly. It's a part of our day. We watch shows like Teletubbies, Handy Manny, Brum (silly English pantomime show with a car), Dora/Diego, Mickey Mouse and of course dearly loved Thomas! I do not let him watch things like Looney Toons/Bugs Bunny type shows with the aplat, bam, whack type animation/stories.
As Deb has said we use it for imaginative play, for instance he plays Handy Manny and we have to pretend something is broken and he fixes it (before he could say Daddy my DS said "Man" when Manny came on

) and although he has few words, his vocabulary includes "broken" and "fix" (and still can't say daddy!!!) He could at 17 months narrate an entire episode of Brum with sign language.
My DS is definitely language delayed, but I don't attribute it to TV as the first words he has learned are from the TV and continues to learn more and more -- though I understand that the language delay that comes from it is that they don't learn interactive, social language.
TV does not come at a sacrifice for other things for him, either. There are rainy days when yes he spends a lot of time in front of the TV though he is playing with other things at the same time, usually with me or DH, but generally we are out of the house playing outside for 6-8 hours of his waking day....when he comes inside from running around the park for 2 hours or being at playgroup I find that 20-30 minutes alone to sit quietly and watch TV really helps him relax and recharge.
I also realise that there would be a LOT of people - professionals included - who totally disagree with my approach to TV and the amount my son watches, but at the end of the day I am comfortable with it, and as far as I am concerned that is all that matters!