Technically, Google would consider them unique pages if they didn't have the same content on them. Google said:
Google treats each URL above separately (and equally) regardless of whether it's a file or a directory, or it contains a trailing slash or it doesn't contain a trailing slash.
But Google isn't dumb and they know "trailing slash and non-trailing slash URLs often serve the same content." So they suggest you pick one and stick with it. Redirect the one you choose not to be your main URL to the other, so if you pick you want a trailing slash, then redirect the non trailing slash. Similar to what I do at rustybrick.com/blog versus rustybrick.com/blog/.
This is nothing new, we discussed this in 2004.
Forum discussion at WebmasterWorld.