Leatherhead
Possibly a Idiot.
I would think that someone who only dips into being a Wizard should just be interested in the utility spells. Only a full-fledged (or almost so) Wizard should be allowed to get the full-powered blasts. Most good Wizards concentrate on control and utility, not on damage anyways (see Treant's guides to Pathfinder for example).
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As Tallifer says, if you multiclass for just a few caster levels, you are probably not using the spells as your primary attack, but for utility. That said, even that lowly fireball could be of situational use if the character is a melee specialist with no other good options for ranged attacks.
If FireLance is correct, and utility scales the same way fireball does (with escalating DCs), then utility spells will be just as useful as a fireball is.
It's setting up to be like 3.X's caster levels all over again.