Julie here is probably the best of the power packs. Honestly every turn you should have your main attacker just copy Julie to get the hypersonic and run around. Overall powerpack is weak team however in something like a 100pt game they might do ok.

Any HSS piece that's 25 points, decent movement, and 10 attack 3 damage is playable as a secondary attacker, support piece harassed. Plus she can share the HSS with a teammate for more move and attack options.