I have heard from some sources that Satmar and Bobover hasidim will not accept Lubavitcher schechting because they believe that Lubavitchers have become idolaters of the Rebbe.
Is this just personal squeamishness on the part of some, or have opinions been publicly rendered?
For the most part, yes.
Postville, Iowa is home to Agriprocessors, the largest kosher meat production facility in the country. Even though the facility is owned by a Lubavitcher, they employ shochetim (ritual slaughterers) from a variety of other sects, and all the products are labelled accordingly.