I wouldn't say that it's a waste of money. It's not very fan-friendly if you're only interested in the WTA, for sure. But occasionally they pull out some real gems, like the Pepsi Grand Slam matches they've been airing. To me, the value in TTC is the re-airing of the classic matches.
As for their coverage of the grand slams, I was excited that they would be supplementing ESPN's coverage until seeing the abominable coverage at the AO. ESPN shows about 5 players three times a day, and TTC then just replays those matches *again* in an edited format.
How many times per day can you watch one freaking match? TTC really needs to focus on matches and stories that are outside of ESPN's "mainstream" audience.
TTC's announcers are awful, too, by and large. Navratilova and Rubin are good, the rest are garbage.