buckworks - 6:13 pm on Nov 13, 2012 (gmt 0)
It's certainly possible to build a successful site on a different TLD.
However, you can be certain that your promotions will bleed some type-in traffic to the dot.com. If it's just a parked page the user would realize their error, but if there's a real site on the dot.com you might never get another chance at that user.
The same would go for domain names with hyphens, if you don't control the version of the name without hyphens.
I'd encourage you to look for a different name where you can get control of the dot.com for yourself.