HDD and online lend themselves to gameplay quite easily through game saves, lesser loading times (I think) and online multiplayer.
Blu Ray discs provide more storage for bigger games with higher viewing resolutions.
WiFi is the only one that doesn\'t affect gameplay, but it makes those online modes easier to use.
With the exception of Blu-Ray, I like those other additions to the PS3. Although I think a 60GB harddrive is excessive and if it would have saved the company or consumer money, I would have gone with a 25 gig, just to be a bit more than Microsoft.