I like Greg's appreciation of the "album" as a format. I'm a good bit older than him, so it's easy for me to share that sentiment. Whether it was the two sided albums of my youth, or the CD's I buy today, I very much appreciate the flow of the songs (and BTW--that's a great formula, Greg. I've copied and pasted it for future use in the unlikely event that I release a whole CD).
In terms of what I like to listen to (and thus, what I'd like to put out someday), I'm cool with 10 songs, but 12 is fairly common as well. In my genres though, a couple/few extended length tunes aren't uncommon, so I also usually see 48-60 minutes of music.
Not the end all, be all--just what I'm used to, and likely what I'd do if I ever get to it.