Personally, I haven't tried too many classes on the beta, but, I found that I liked Combat Allies better for the classes I DID try (which would be DH, hunter, and warrior). For instance, as I stated earlier in the thread, Akama is a nice bodyguard in terms of damage for DHs, but he tends to knock enemies around with his lightning attacks. That's not very fun for a melee class. Altruis, however, is a Combat Ally, and he simply shows up and does an AoE randomly during combat, which did a TON of damage. However, there were times I had important missions, and couldn't even really afford to have a Combat Ally with me anyway.
For the record, if you didn't choose Altruis, you can choose Kayn Sunfury, and you get the Shade of Akama. No real difference in terms of combat at all, just different voice lines during combat, and the story changes ever so slightly due to your choices (but not too much, overall).