I've been experimenting with different antennas and pre-amps for the good part of 2005, and I'm in Kitchener, near the riverbank of the Grand River overlooking Cambridge.
Nothing is 100% consistent, but it's very rare if I can't pull in more than a few DTV stations on any given evening. I have to rotate more northwards, away from Buffalo, if I want to watch Toronto stations.
I have a ViewSonic NextVision HD12 set-top box:
I have experimented with both a new Channel Master 4228 with 7775 pre-amp and a Winegard PR
-9032 with AP-4800 pre-amp, and found that the Winegard gear is better, both in reception and manufacturing quality:
I've even played around with an old 5 or 7 foot parabolic UHF antenna that's on a rusty old 20 foot tower on my grandparents old house, and it's proven surprisingly good for ATSC reception, too.
To further prove that "yes, there is DTV available OTA in Kitchener" I should state that I have around 200 feet of cable between my antenna and receiver, due to some 75 foot tall trees obstructing line-of-sight on half of the property. Granted, I'm using a long piece of hardline aluminum-clad cable TV distribution trunk that I've had kicking around as scrap, as well as some RG11 and a bit of RG6, but that's nothing magic. I tried using RG6 for the full-length but it killed most of my signal -- too much cable loss.
I'm also located close to a Hydro One 115kV transmission corridor, but this seems to have little affect on things.
I suppose I'm lucky in that I'm fairly high on the horizon, at least as far as elevation is concerned... I've had surprisingly good luck playing around with an antenna on a stick only 12 feet off the ground.
One thing I discovered is that these UHF channels seem to require
that you have a pre-amp at the antenna, no matter how short the coaxial cable to your tuner may be. I've also noticed that reception of analog UHF channels originating from the same transmitter tower site does not directly corelate with reception of HDTV channels -- for example, sometimes I can be getting relatively poor reception on channel 17 (WNED Buffalo) but channel 43, their digital equivalent, can be perfectly fine. Of course, with digital, you usually either get a perfect signal or no signal -- tiling/breakup only seems to occur when you're right on the borderline signal-to-noise ratio.
I think you basically have to take your chance and buy some equipment and play around with it. There's no definitive "yes" or "no" answer as to what you can and cannot receive, here. I can't speak for older/cheaper (less sensitive) 8VSB receivers... they might not be able to pick up as many channels.
If you want some specific examples, I can almost always get CBS and UPN from Buffalo, since their transmitter is 1,000,000 watts. Sun TV (from Hamilton) is easy to get, too, since they're on a 'low' channel -- 15, so there's less cable loss at that frequency. CBC Toronto comes in easy, and CTV Toronto is a little less reliable. NBC, ABC, FOX, and PBS from Buffalo are all about the same -- hard to get during the day, fairly reliable reception in the late evening. Citytv Toronto is almost impossible to receive -- their antenna is too directional, and "WB49" (DT) is ridiculously low-power, so I've never received that. SRC (CBC French) Toronto comes in the odd time, too.
Once CH (Hamilton) gets their transmitter going, I anticipate that will be easy to receive, too, but I don't know what to think about Global Toronto and OMNI.1/OMNI.2 since they're going to be low-power.