They have a charging station where you can charge with the silicone covers on. I forgot what it's called but someone recommended it on Slickdeals when there was a Nyko deal.
I thought about it because after my friend "borrowed" 4 rechargeable AA batteries from me and I put another 6 into my Wiimotes, I only have TWO free in the whole house now. Just the other day my guitar died midway in Guitar Hero world Tour and I just swapped them out on the spot. That made me think I can't afford to use a charging station because that implies downtime.
I say go for rechargeable batteries. What are you gonna do when your Wii dies and you're having a Wii party? Tell everyone to get off while you recharge?