One has to be careful, especially given the quality of many sources on the internet, which sometimes resemble the Weekly World News more than any reasonable attempt at research. I don't know what you would call a "Christian perspective"; Christians may be just as ill-informed and hysterical as anyone else.
Anyways, the Opus Dei organization is meant to be a lay Catholic organization, and is very conservative in character. In some regards, it's organization is similar to a monastic order, as some of the members may choose to live in a communal environment although they still work in the community. The idea is that while the more traditional teaching and charitiable work done is valuable, there is a need to foster a "lay spirituality", which means members working in more secular professions and bearing witness to their faith.
As for being "cultish", I have seen nothing to indicate that they're any worse than the more established orders. Being a human organization, it is made up of, well, humans, with everything that that entails.
An article of some use my be found at:
http://abcnews.go.com/sections/us/DailyNews/opusdei_story1.html
http://en.wikipedia.org/wiki/Opus_Dei
And of course,
http://www.opusdei.org/