If you know what you are looking for, you can see a lot more at a race. This isn't easy. It is easy to turn up, sit down and watch cars go around but if you really look you can find things that the tv never notices. At the hairpin at Montreal you can notice which teams constantly lock up early under braking (are they running low wings or have they screwed up the balance), you can notice which teams lift up their inside fronts at the apex (plenty of roll in the setup, soft suspension settings and therefore probably plenty of wing) and during the race you can notice which cars are sliding into the corner (front tyre wear) and which ones take a fraction of a second longer to get on the gas (rear tyre wear).
It can be annoying to only see a fraction of the circuit but with big screen tvs and now with fan vision tv you really don't need to worry. Fanvision, for those who don't know is a portable little tv screen. With it you can watch the race on screen, choose any onboard you like, watch the live timing, listen to commentary and team radio. So long as you don't treat it like you have come all the way to the track to watch tv it is invaluable. I left it on the timing screen for the duration of the race, so you know instantly who has decided to turn it up and by how much. It adds a lot to watching at the track.
Lastly (although I could keep on going here), the great thing about being at the race live, is that you are there for three whole days amongst like minded people who love to talk about the sport. Belgium has the added bonus in that you also live amongst them in the camp site. Each year I go to the Grand Prix with a group of friends that I met in the stand and who I only ever see trackside. We spend three glorious days living out of each others beer coolers and wallets. There realy is nothing like a live race. If you haven't been, then go.