Well for one thing you get to record programs with windows media center that must be purchased for the built in TV tuner to work. It's not the best record quality, but it is built in so if you real wanted to just record in good quality probably just get an external TV Tuner. I got the option for my 9880, but I have not used it yet. I guess it will come in handy eventually, but have not had the need to test it out yet.
Really I would use the money and get more ram, a better processor, or some cool accessories. Don't worry about if it is good or not, if you have a need for a tuner later you can just buy one in the future. If I did it over again I would have used that money for something else.
What other options are you looking at?
If you get the tuner will you be sacrificing something else?