My opinion GLSDB

The biggest weakness i see is the speed , original bomb is rated or max 2 Mach
There is 0 official info about its speed i found fishy

Its going to slow down 1 Mach or much slower in the end phase the longer it goes the worst it gets . Basic air resistance and glide physics

It has still a low RCS but because the wings it can be detected earlier then HIMARS

GLSDB vs HIMARS

Speed : much worst
HE : same
RCS : worst
Range : twice better > more targets
Air defense survival : worst

Most important to counter is good low alt (masted) radars , and lot of integrated SAM
TorM1-2, BukM2-3,Pantsyr all can shoot it down in range
If early warning is good SAM can be alerted,switched on and focused in time

Against well defended targets it will struggle like Crimean naval and air base ,Belgorod etc.
Not defended places and front line will be a problem for russia (arty threat push SAM cover back)

Adding to the long threats like the suicide drones, will be costly to cover everything
A new HYPE for the ukrops to move on from like Bayraktar drones
Every PGM can kill people very well already

missilewars

Zaprozhec is on the menu, ukrop arty exist but rated low

We know more tomorrow, what they took exactly
Doesn't looks like just a probing attack , they want to take many km size pieces as possible taking advantage of the ukrop reserves are decimated in Bakhmut and the defense seems faltering there
(more pressure the better)