I discovered today that thanks to the USGS metadata format update on August 29, the new Landsat metadata files (*MTL.TXT) are not readable by ENVI via the "open Landsat GeoTIFF with Metadata" function. They do, however, include the old format MTL files as "*MTLold.txt", which are readable by ENVI. They've also modified the actual filenames to match the subdirectory names in which the data are distributed. Yes, this means you may have to update your code if it involves opening up Landsat imagery from IDL or via Python/ ArcGIS.