I'm a Brit that did Iran last summer, no issues whatsoever apart from one cross examination at one checkpoint where they wanted to know where i'd been every night, my tracks on my gps, computer files, maps etc,, but in retrospect this checkpoint was near the uranium enrichment facility... oh well!
Other than that generally treated like a vip by civilians, cops the like- tea, ice cream, fruit, I only stayed in hotels for 1/3rd of my time, the rest was in people's houses.. and even then I could have made it 100% of the time, I just on occasion wanted some peace and quiet as the Iranians are so inquisitive about tourists as they don't get many as you can imagine.. Some were surprised to see me so covered up but the tourist women I met that didn't cover up were getting a hard time and quite rightly so if you can't be bothered to do a little research and be culturally observant... not excusing the people giving the hassle but come on, its the law! I would react strange if someone walked naked down my high street and this is a close comparison. But as a woman generally I had no problems and found it fascinating.
I shared a room with a chap on occasion and they didn't bat an eyelid that we were not married or together.. even in Qom, apparently the most conservative city. The most annoying thing is bikes/cars driving dangerously to film you or look at you, they will weave in and out of traffic up to 150kph, no getting away from them. :-/
Iran was one of the highlights of the trips
Hope this helps..
'Life begins at the end of your comfort zone'-
UK to Asia on a DRZ400 2012-2013