Skitarii as a faction I could take or leave, but it's an encouraging trend. Between the harlies and Skitarii we're expanding from the core races, and while I'm not sure we need yet another set of imperial forces they at least have a different silhouette and aren't just another set of bloomin space marines! I'm hoping that they'll start looking more seriously at the bad guys soon though.
(from here on this is part rant, part wishlisting, feel free to ignore)
Between inquisition, marines, Sisters, IG and now admech the imperial forces can ally to cover almost every base while the 'nids suffer from a sub standard codex and no chance for proper allies. Chaos has also been a bit lacklustre for the past... 10 years? but now we see the possibilities of some interesting factions coming out of it rather than just getting a book to gether together a bunch of themed units from existing books. For example Cult lists, maybe led by some marines who's armour have broken over 10,000 years? Traitor guard with some demon support?
These guys are supposed to be the big bad of the setting, but I don't know anyone who's remotely interested in playing them.
We've also got Genestealer cults, Zoats, Tau empire subraces, Exodites, Grot rebellions (oh please!), demiurge, the list goes on and on. Even if they're not huge releases we should try to get to the stage where each big codex has at least one allied sub codex (although what you'd put with the necrons eludes me for the moment... any thoughts?).
I've always been of the opinion that the xenos races don't get enough support in terms of releases (and to be fair, why bother when there are all the space marines chapters sharing kits) but some get it worse than others.
I'd really just like to see each of the other races get half as many options as those playing imperials have, and I'm really exited to see these new smaller codexes come in and seem to be giving us that opportunity!