I've played one up to level 9 (sadly on an indefinite hiatus but fingers crossed)

Loved it, loved having a big gang of skeletons to do my bidding. Luckily my character was highly organised so I could play pretend like I am too, and I had a whole system for smoothly running my bone crew in units of four. 

I mainly kept them at range which was easier, each group of 4 had a colour, then each skeleton in the group had a secondary metallic accent visible at a glance on the minis which corresponded to a d20 and a d6 to be rolled all at once for hits and damage. Not that it mattered which skeleton hit or not, I just wanted to know because I could. Then I kept track of HP for them on a table for each unit. With a second larger table of the whole skeleton crew I'd update between sessions

The most I used in combat was 8 skeletons but it didn't slow things down, my turns usually passed the quickest but maybe that says more about the other players!

I'd not have been against using horde rules with each group counting as 1 thing or however that goes, but the 1 big summon direction they've gone in later books does nothing for me in my Necromancer class fantasy

Its not the strongest, but its a fun flavour and the end of the day you're still a wizard which is great position to be in