This issue obviously depends completly on the social contract you form in the relationship. If you date the nic girl you met during the catholics bakery sale, "cheating" will probably a no-go in the relationship.
But the funny thing about your question "Cheating in relationships: your views" is, that it already answers itself. If the act is labeled as cheating, you already mark it as something negativ. While some things that are usually considered cheating can provide positive things to a relationship.
Like relief of sexual desires, your regular partner can't or doesn't want to meet. Say you absolutly crave a certain type of sexual intercurse, your partner finds disgusting. What would damage your relationship worse: a) Living with It, surpressing it, eventually giving up a part of yourself b) trying to convince youzr partner to something he/she doesn't like or c) hopping in bed with someone else or a professional every now and then to get relief?
You don't even have to meet this question on a sexual level. Some people consider talking with persons of the opposite sex cheating, we thing that's strange, because it isn't part of our default social contract for relationships, as is having multiple sexual partners. Only if you extend your view beyond tihs concept, you can really argue about this question.
To give a nice conclusing example, from real life and not the cold, harsh world of philosophy: I once had a relationship with a nice girl, lasted to years and ended in mutual agreement, because logistics had become too difficult. When I first met her, she soon stated, that she likes sleeping with multiplie people of various sexes, religions, numbers and skin-colours. At first I was pretty stunned, but once it turned out that she handled that in a very smart way, seeing it as some kind of sport or hobby, and that she was very cereful about any kind of STD, it really wan't a problem anymore. She stated the acceptance of this fact as a foundaion for the relationship, so you can't call it cheating.
Sex should not be, what determinates your relationship, if it is, you are doing it wrong.
When thing about it the whole concept of single-partner-relationships is kind of out dated. "Till death does us appart" was made in times whre people married at 15 and died at 30, spend most of their time working under horribly conditions. Today people are expected to live 80 years and longer, whithout having become twice as reli- or likeable.
