Depends on the unit and/or mission. For those heavies with some kind of TWCF funds (C-17, C-5, tankers to a degree), bumming is possible but I've heard it's been curtailed to a degree. For fighters, those with an alert mission have more bumming opportunities than those without.

I'm in a Herk unit, and for the most part, Herk squadrons have been hit hard by the cutbacks. The AR ANG at Little Rock has the FTU mission and it's the only Herk unit that I know of that has regular opportunities to bum...but you gotta be an IP first.