I looked at that and yes the fan does run faster and push more air, but the "extra noise" you speak of does not exist on my TiVo, so really the only expense that exists for me is the extra heat the unit has to endure. A unit that runs at 43C which mine was running at, once converted is 109.4F and with the new fan its running at 35C converted to 95F which is a difference of 14.4F degrees cooler. Also I have upgraded to a WD Green 1TB drive, also completely silent with AAM settings tuned to 80h (128).
Anyone that knows anything about computers and electronics can tell you that heat is the worst enemy for these things. If you're fine with 45C then I'm happy for you. If I can run mine at 35C and possibly save mine from the heat and still have a silent TiVo, then I'm ecstatic. I've been looking for a cheap way to cool this thing down since I bought it. A hard drive in a computer runs so much cooler, why cant a TiVo?
I wouldn't say that TiVo has anyones best interest at heart. If someones TiVo doesn't last very long, then all they are going to do is sell more TiVo's.