I've spent the majority of time on the XMB so I'll have to vote for that, I'm most used to it after all lol
that said, it's far from perfect and could do with a few simple tweaks like the ability to hide icons, change the XMB to vertical layout, grouping of media (especially music) in a similar (a-c, d-f etc.) way the PSN lays out multiple content

Proud Sony Rear Admiral







