In theory, your antenna should be fine. Basically, if you get good over the air reception now, you should have perfect digital reception. The only difference is the picture will be super clear instead of snowy once you go digital... right about dvd quality... or if you do free-to-air stuff, more or less the same quality you get out of fta.
I just bought a digital tv with some Christmas money + a little bit extra and am amazed by the quality. One thing I really like is the ABC channel here used to be super fuzz since it is a little further away than NBC and CBS and PBS towers... Now that it's all digital it's crystal clear, just like the other digital channels. Something also that's very nice is they can fit subchannels in, so now I can get the local Fox Channel since it's a subchannel of ABC and get MyTV since it's a subchannel of the NBC affiliate. I used to never be able to get either of those. Fox is analog too, but it's channel 36, so is darn near impossible to pick up way out in the sticks...
... and on top of that both ABC and NBC have subchannels dedicated to weather 24/7... very nice, very nice indeed.
Now I just have to figure out how the hell to get coax to spit to feed decent analog signal upstairs... at the moment, I've got rabbit ears up there since splitting coax via y branches is losing lots of signal since there's another 100 foot of coax involved, roughly...
but, I think once I get one of those snazzy digital to analog converters for up there, in theory it should all be crystal clear too since there is signal there, just not very strong signal... so in theory, if it's just enough signal that it can be converted to digital, it'll come out all good.
I don't really want to buy a new vcr or stick with having vcr stuck on one channel at a time, so am trying to get my hands on an digital hd pci card to handle the vcr dirty work for me. I bid on an ebay one, but it's got about a week left on it, so will wait and see what happens.