can it be used in the microwave?

Yes and no. Yes it can be used, and it will work just fine, it is the same material Nalgenes were made out of until recently. The no part comes from the risk of BPA leaching in something like this. Lexan is generally safe, and so far research only shows that the BPA is leached in significant amounts when it is heated. So it can be, it just may not be the best idea to do so.
View Details: GSI Outdoor Lexan Cup - 12 oz >