While yes, your familiar would only be missing out on 5 NA, Spell Resistance, and Scry on Familiar, which, while nice, shouldn't be dealbreakers.
Oh, and 5 points of intelligence.

Admittedly, you do miss out on the familiar spell epic feat for free at level 21, however...

This restriction also applies to pretty much all arcane prestige classes as well: A wizard 5/Incantatrix 10 would have a familiar as a level 5 wizard, because incantatrix doesn't give a familiar.