I actually went to Tehran in 2000 (oil & gas industry related trip), and it wasn't a bit like the anti-Iran propaganda machine would have had me believe - everyone I met was really friendly, and nobody seemed particularly conservative or over-zealous in their religious views. On top of that, the food was incredible, and lots of people even spoke great English!

Iran is also home to many historical sites - if politics were different, it would likely be a popular tourist destination.