No its not a big mistake but if you mostly rent, you would need to think hard where to get new HD movies. Maybe we all will switch to Blockbuster online (the store doesn't carry HD DVD). But who knows blockbuster will stop carrying HD titles in the future.

I'm not going to buy all the HD DVD movies just to watch once and store in the case, renting before buying is my choice but now with Netflix going blu-ray, I will have to think twice. I have a few HD DVD titles in my queue and they are all Long Wait or Very Long Wait, I read from another forum that some of the HD DVD titles were vanished, guess netflix doesn't stock anymore when people return them scratched or broken.