There still aren't any signs it really matters though - have a look at Metacritic for a non-biased look at how the 360 games suffer from not having a HDD.
And to drag this back on track - the same can be said for the HD-DVD.
It´s hard to see the difference because the games are designed to work with a harddrive. And i with the current standard of reviews i would doubt how deep they actually go into testing a game on 360´s without Harddrives.
The same goes for DVD vs HD-DVD based games.
Is PGR 4 a bad game because there isn´t space for another track or 3? Absolutely not, would it have been more value for money with more tracks? yes. Would it have been included if the space was there, maybe not