The religious make-up of the new 111th Congress generally reflects the religious diversity of the American electorate. Protestants make up the majority of Congress with 54.7% (compared to 51.3% of the American population) and Catholics make up 30% (compared to almost 24% of the American population). Jews make up 8.4% (1.7%) of Congress while Mormans make up 2.6% (1.7%). There are two elected Muslims and two Buddhists, but only one admitted atheist, Rep. Pete Stark (D - Fremont) - professed atheism or agnosticism is still considered political suicide.
Diversity, to me, is always a good thing, as the exposure to different people and ideas increases dialogue and progress. Keep in mind, however, that the diversity of the overall population is most likely different than the demographic breakdown of each district/state. And when Representatives of districts with overly unrepresentative samples team together to write or vote on religiously-implicated legislation, someone is going to be upset, even marginalized. As the last decades have shown, religious diversity in Congress does not mean tolerance in legislation.