That would be about Mach 10 weapon launch. I don't think that's been seriously studied or tried in practice. That would be quite a technological achievement all by itself, aside from everything else the thing can do.

Of course the vehicle is going to be destroyed anyway, so just carry the payload all the way down till it goes boom or whatever, unless you were hoping to launch multiple warheads. The problem is the whole vehicle is very light, so you're not going to fit a B-52 worth of payloads in a vehicle who's launch weight is, I believe, lighter than a GBU-43. My point being that if vehicle plus payload at launch is lighter than a GBU-43, there's not much point in being concerned with how many GBU-43 it can be dropped if it can only carry a fraction of one anyway.

The main problem is its hard to think up a mission profile where a cruise missile wouldn't be cheaper and more effective.

I'm not an expert but I will state that x-37 in orbit doesn't have 23km/s delta-v. I think wiki for similar vehicles can confirm that: http://en.wikipedia.org/wiki/Delta-v_budget

Its a hydrazine monopropellent, or so they say, so an Isp of 250 or so would be impressive. Someone with a lot more time on their hands can tell you the mass fraction required to get 23 KM/s outta a 250 second Isp and its going to have about as many 9's as reliability marketing material. So yeah, thats not happening.

Don't forget aerobraking which can knock a big chunk off that delta-v.