Hmmmm... ...
The thing is... getting to level 19 in the game as a soloist is a 'piece of cake', especially if you are a veteran soloist and know how to maximise your XP gains in the early beginnings.
That said... there are other ways to counter Magic Missile, Skull Trap and Abi-Dalzim's Horrid Wilting.
I recently replaced Friends with Shield. Good in the beginning, it stays useful even towards the end game due to one property. Immunity to Magic Missiles.
Skull Trap and ADHW can be countered with Mirror Image, or Spell Immunity:Necromancy if you want to be 100% safe.
Sad to say... but there are very little good( or uber as I prefer them) spells at Level 8, especially ones that cater to my kind of playing style( speedcasting).
Level 6 spells on the other hand... have a lot of useful spells, and it would be a shame to 'waste' a slot on one spell, when you can easily get a much better spell at Level 8 with next to nothing penalties.
The Belt of Inertial Barrier is more or less welded to my Sorcerers,
so everytime I cast PfEnergy, I heal from Magic Damage( 25% of Magic Damage done to me). 95% resistances to Fire/Cold/Electricity in ToB is nothing to sniff at either, although Spell Immunity:Evocation handles most of the elemental damage issues.
I do use PfEnergy often, if only to laugh at the Improved Mages who wildly cast their ADHWs/Skull Traps and wonder why I can just shrug them off; and of course... I use my Project Image to cast it on itself and my Sorcerer before unleashing the so-cheesy-it-is-almost-unfair tactic of Bunny Nuking the enemy.
[img]graemlins/hehe.gif[/img]
Just make sure that there are no innocents in the area( read, THE MAP), unless you are playing a Chaotic Evil/Neutral Sorcerer or something.