So Blood Angels suddenly have Mephiston turn into a FMC for a turn, Lysander makes his Terminator Titanhammer T5 and becomes T6 himself, Word Bearers can just steal a Green Tide or Emperor's Fist Tank Company for a turn, and Dark Angels... get rerolls to hit, on their basic small arms, that they either had already or don't get to access? Basic Bolters, if you care about them being twin linked, will have Divination, Ravenwing are already Twin Linked, and Terminators get no bonus. RAW, of course, every single PA model gets twin-linked because they're technically all armed with Bolt Pistols but Hail of Fire only specifies 'their weapons become Twin-Linked', not just their bolt weapons, but this still sucks.
Not that there's too much to complain about - Night Lords get Fear, and some shitty leadership rerolls, Alpha Legion get IWND on... their HQ choices, Obliterators and Spawn? And Death Guard get Feel No Pain and Fearless on all of their Plague Marines! As well as of course the Librarius pooping out a Str D AP1 Large Blast every turn with rerolls to hit and wound allocated as per barrage, so I'm fucking pleased about that I can tell you - Marines are FINALLY balanced in the super-heavy stakes without having to buy or sculpt or transport a bigass Thunderhawk with the new monopoly on Vortex.
Overall, I think Finest Hour is pretty cool, even if some of them would only be 'good' on the basic Warlord charts, let alone the epic nature of Finest Hour. The Dark Angel, Night Lord and World Eater ones could probably be put into the Warlord Tables for those who don't mind using homebrew (although I'd probably shorten the range; in the case of Dark Angels, make it a 12" bubble).
Don't forget that Finest Hour only lasts like a turn.