Well, back in Exile simulclarum was actually useful.
In Avernum, it just got worse and worse.
By the time you get to Avernum 3, I personally thought the spell was next to useless.
Theres no point summoning weak creatures with this spell, and strong creatures not only require large chunks of SP, they dont last long (I havnt played A3 in a long time, but IIRC I stopped using Simulclarum after I realised the creatures I summoned tended to dissappear after 3 rounds. Actually, that was probably A2.), and they have practically no real effect on a given battle (You can just slaughter everything yourself). Plus, unlike Exile, you cant capture the soul of particularly cool creatures (eg dragons), not to mention that the spell is a hostile one, which notches its usefullness down yet another level.
Having said that, I have just checked my save file and I had:
Gazer
Dark Wyrm
Hakaai
Efreet
IIRC I practically never used them, but it seems plenty of other people use them to great effect. Whatever floats your boat I guess.