Joint Tours have semi officially been promotion or command requirements at the O-5 / O-6 level for quite some time.
There are a slew of other branch LO's or SME's in all element Commands or regional commands - so getting Joint time isn't an issue.
The Staff NCO aspect is generally new though - I suspect it is part of Pete's "Everyone a Gunfighter" mentality to push folks (he's taken some indirect shots at the VP) from trades or branches into 'seeing what the Infantry is like'.
Generally I think cross pollination is good, but I have a few folks I know that took it as a way out the door.
I had a buddy who was an 18A O-6 who had to sit for 2 years at a CIA Desk before he was looked at for BG, all it did was have him take another Masters on the side and get out as he wasn't really a sit in the cubicle sort of fellow. West Pointer, and with multiple valor awards - he decided if he was sitting behind a desk - he wanted to make money while doing so.
Another person I knew did a tour in SOCOM (he was an O-6 Surface Navy non SOF fellow) and he used his TS SCI and the SAPS's from that to get out and work in Industry.