The range summoning gives you means you could effectively place a unit 12" from a current character. On its own, that character is unlikely to get that distance unless it's got a jump pack. Dropping a tough unit on objectives with this extra push is helpful. It is also very useful for gaining access to specific units if you don't want to lose CP
on a detachment. A Master of Possessions can do this much more effectively with a psychic power.
So far in 9th, the only thing I've summoned is a Poxbringer for the psychic power and buff to NURGLE DAEMON Marines. In addition to the useful support roll, he has been an extra body that I was able to summon onto an objective from cover.
Edit: it's also worth mentioning that when you set aside your points for summoning, you don't need to assign them to models. They are not typical reserves in that manner. They do not exist until you summon them, at which point you must spend the reserved points to bring them into play following the rules for Daemonic ritual. This also adds an element of versatility. The overall usefulness of said versatility is debatable, but you could summon psychic support, you could summon a wall of bodies, you could summon a squad of bloodletters, you could summon something speedy, you could summon a melee monster and you don't have to decide before the game. In 8th it was widely considered better just to take a detachment of Daemons but in 9th you are penalized for doing that, so summoning is comparatively better now.
Edited by Doom Herald, 07 September 2020 - 01:23 AM.