At one time one of the main problems with an LED TV was that the backlighting was not of a very high quality and this was enough to put many people off buying it. Recently there have been many improvements and they are getting closer to the standard of a plasma TV. The viewing angle has improved and is now at 75° and there is no loss of contrast level with some of the better models.
Black levels used to be an issue but this is another area where there has been a lot of work done to prevent it being a problem. Brightness is always going to be an issue and if the picture is dark few people will enjoy watching many programs as a lot of the detail will be lost and it could be that a vital bit of information could be missed and the whole point of watching the program spoiled. Florescent bulbs that have been in use in the past are not as good as the current system that is LED based LCDs. Color is also going to make watching a program more enjoyable and with some TVs this is an aspect that becomes damaged over time. LED is providing a longer lasting high level of color than LCDs.
The lifespan is one of the major reasons why LED TV sets are becoming more saleable as there is less chance that they will need to be replaced in the next couple of years. If you buy a television you like then it should be in the living room for a good time until the latest developments appear in TVs on the market.
There are a few disadvantages and one is that an LED television is going to be less economical to use as it will use more energy to run. There are as yet no ways to bypass this as the extra electricity used is needed to provide the areas that are covered in the pro section.
Size is another problem as many of them are made in such a way that it is not possible to mount them on the wall, although if this was never the intention, that will not be seen as a problem. Cost is going to be the most prohibitive of all the issues as it will cost a lot more to purchase the LED TV.