I'm on the whole pretty positive about this. Unlike other MMORPG stores, the items don't affect game-play. They can still be bought IG for IG currency, or at the store for IG currency converted to plex converted to aurum. Yes, those willing/ able to spend large amounts of RL currency to buy plex will be able to have more stuff than those who don't, but that situation currently exists at the moment (buy a titan alt! buy a titan!)
I think the pricing of items will affect how well it works in practice.