In theory, it should not make matters more difficult. In practice, it will depend on the person you get at the interview, as well as your overall appearance
On the Norwegian version of Flyertalk, at least one person (ethnic Norwegian/Scot) has reported about the interviewer clearly not liking the fact that he was in Iran, grilling him intensely regarding the visit, and subsequently refusing him a visa. The next time, however, he apparently got it after some questions about what he did there and what sorts of people he dealt with.
In general, it is a fact that dressing well and having a stable job will go a long way.
Expect to be asked about what you did in Iran and whether you dealt with any religious figures. Like I said, they could very well give you a hard time, depending on both who you get at the interview and your overall appearance, but the best thing you can do is be prepared and answer the questions confidently and truthfully