Just wondering whether there are any spells that were in the earlier Wizardry series that you miss in the later games?

For me, the best examples are MALOR and MADI. Malor let to teleport to arbitrary locations and was incredibly convenient.

MADI is missing in Wizardry 6 and 7, and it shows when you get to high levels. At that point, you may have a lot of hit points, but there's no way to heal them. Heal wounds averages only 31.5 points at power level 7, which isn't much if you have over 300 hit points, making healing tedious. Healthfull averages even less. (Really, that spell feels rather pointless.) Restoration (Wizardry 8's MADI) doesn't exist, and neither does MAHAMAN (which would be another soultion, even with the level drain drawback).

Any other spells that you miss in the later wizardries?

Wiz8 helps somewhat with the "cast until done" power option when it comes to healing. I actually don't remember whether that was in 6 or either version of 7...

The problem is that you can only return to the last place you set the portal. In particular, this means you can't teleport to a place you haven't been, as you could in early Wizardry. Also, you didn't have to manage portal locations; all you needed was the coordinates (and the targeted floor (or portion of floor in Wizardry 5) has to allow teleporting).
Furthermore, Wizardry 6 and 7 are still left out.