We have done GF for a few years.
How quickly you receive games depends on how close you are to a distribution center. They should offer a free trial (I think ??), and that would be a good way to estimate shipping/receiving time.
New releases and popular games are sometimes hard to get because of demand, so there can be a long wait for those games (like with Netflix).
If I am not mistaken, Netflix and GF are the same company.
We have awesome turn around time with Netflix and lousy turn around time with Gamefly, but I think the Netflix distribution system is local for us (Waco, I think? I can't remember) and the GF one is in California.
Since you will be renting primarily Wii games, it may not be as big a problem for you since there may be less demand for Wii games. I could be wrong about that though!
We have the 3 game plan for about $32/month. It's a little pricey, but still cheaper than buying games. GF will also give you reward dollars and other incentives to use as time goes on. They also sell used games for a reduced price.
My husband beats games pretty quickly, so GF saves us $$. The boys don't usually get games from GF. They usually get their Wii games as gifts or earn them, so their Wii library is not huge (they've had their Wii for about a year and a half and they only have 7 or 8 games, haha, poor kids!). They play games over and over and my oldest will unlock E-V-E-R-Y-T-H-I-N-G. LOL.
Anyways, I was looking over GF and the cheapest plan is 1 game out at a time for like $16 plus tax. 2 games is $23 plus tax. To do the 3 game plan, you have to be a customer for 2 months first, then you can upgrade to that plan. The 4 game plan is $37 plus tax, but it also requires 2 months of good account standing.
HTH.