I've always had some issues with Netflix and Tivo Transfer with my two Series 3 Tivos. The Netflix would lock up sometimes or the online menus on the Tivo would be slow. I've considered using a powerline system, but they were kind of expensive.
I bought the Actiontec Plug Av 200 Mbps adapter kit, and I am amazed. It was $50 on Amazon, but it is worth the extra speed without having to run internet cable throughout my house. I wish I had done this sooner. I know they don't work for everyone, but they worked for me right out of the box.
I could never watch a program right away that was transferring from another Tivo, but I can now. The amazing thing is only one of my Tivos is hooked up to the powerline; the other uses wireless still. I'll probably get an adapter for that one as well.