I agree with everything other people have posted... Right now they're not competing very well with bricklink prices on a lot of parts, and I'm afraid that won't change. So it would be best to flesh out the selection of parts where they can
compete on either price or availability: animals, minifigs and accessories(food, weapons, coins, etc), foliage pieces, and new/rare colors.
I would also love to be able to get large quantities of parts (especially basic brick and plate) at lower prices, hopefully much closer to bricklink prices. If there's any way they could make that happen, maybe by offering "by the kilo" pricing, or by the box, that would be great. I can't be the only person on CC who would buy several kilos of gray bricks, if they offered them at a competitive price.