Should I get tivo or stick with cable?

I currently have Service Electric Cable TV. I am, like most, looking to save money here and there on monthly bills. I see that Tivo has a deal going on right now. $99 for the Tivo Premiere plus $19.95 a month with a 1 year contract. I am new to this tivo thing. I currently pay 123.00 a month for cable plus internet and I have cable in 4 rooms in my home. My question - does anyone have tivo and if so, is the $99 charge for the box a one time thing or a monthly rental? Will they break up that price on your monthly bill? Do I need 4 tivos in order to get cable in the 3 bedrooms and the living room? I also know I need cable cards from the cable company. The rent them at like 2.95 a month. Does this take the place of having cable service through my current provider? I am so confused and can't seem to find a definitive answer online. Does tivo do internet? If anyone out there switched from cable to tivo to save money can you please let me know how easy it was and how much you saved? Sorry I am a tivo dummy....Thanks for your help