I installed a Wii LAN adapter hoping the same thing. Sadly the Wii LAN adapter does not work well at all with WiiMC (maybe I just got a bad one) but yea. It is slow as tar loading up and the directory listing for Samba gets garbled and only shows a handful.
Not sure if this has to do with the USB module WiiMC uses, but yea. I would save your money.
As far as buffering issues, if your router has QOS, set that up and give the Wii Priority, this should alleviate that.