While I have never actually tried it, I would expect that you would see a signal loss by using a generic Y-adapter. It may not be visible with a single Y though. I have split composite 3-ways before signal loss became an issue. But, that was to low quality displays instead of decent TVs. Now, with my component that I do split to my plasma and my projector I use an Extron RGBHV distribution amplifier. This is similar to what you linked to at SmartHome.
I have an offer if you need to send your video to a couple of TVs only. I have an extra Extron piece I could let go for 50 bucks if you want it. It is very similar to this piece:
http://www.extron.com/product/product.asp?id=in3252hr&subtype=32 and the one that I am currently using works perfectly. Extron stuff is top notch and is a professional standard seeing little use in the home, but nearly impossible to beat in overall quality.