Your going to need:
All TVs to be the same brand (use the same IR codes)
A USB-UIRT or VCR Commander( won't work with some newer TVs)
I don't think using a few different "brands" of TV's should be a problem. Although I've had problems with the Sony brand and the VCR Commander myself. Since TV's do "toggle" (same power signal is used for On as Off) extra checks or efforts will need to be made.
I use a
Trickle-Saver on my living room TV. The trickle-saver powers a walwart that activates a powerflash module. The monitored status of that PowerFlash module tracks the status of the TV. This allows my morning macro to turn my TV On when I first set down to watch the news and drink coffee. But then.... the HA PC can
see the TV is on... when I get up refill my coffee and return to the chair.
So the TV On Macro isn't repeated. Something like that might be helpful in such a setup as well.
I know this setup is starting sound a little complex [and Cocoontech-like] but
I think it is very do-able. And with the cost of electric and the current American energy saving tax cuts.... it is darn well worth the effort as well.