I ditched cable over 2 years ago and got an over-the-air digital antenna and built a Home Theater PC. I use this (
http://www.amazon.com/dp/B000EHUE7I/?tag=atomicindus08-20) Antenna Direct DB2 antenna and this (
http://www.amazon.com/dp/B003B99KDK/?tag=atomicindus08-20) 8-way Coaxial Amplifier. In total, I spent just over $650, including all the cable I cut myself, the PVC antenna mount, the amplifier, antenna and HTPC. Saving myself $60 a month in cable bills, I've paid for it 2 times over already. If you just go with the antenna and amplifier, it'll pay for itself in 3 months... with just the antenna, it'll pay for itself in 2.
I now use Netflix ($8 a month for streaming) and the online websites. For instance, during March Madness, I could watch ANY of the games live using the March Madness Live website. For 'Premium' shows, I actually download them. Add Hulu and/or Amazon Instant Video (free if you pay for an Amazon Prime account) and there isn't much you are missing. With the Home Theater PC, I added coaxial in, so we actually record shows using Windows Media Center (anything that comes over the air, which is CBS / NBC / FOX / ABC... though I get about 30 channels in total).
Also, the BIGGEST issue with switching to OTA antenna from cable is typically sports. Not all sports come on the big 4 stations above, so if you watch tons of ESPN, antenna is probably not your thing.