I also only went to Sunday. The infrastructure of the event was great, but the lineup was awful compared to the last two years. Saturday was a collection of every pitchfork band I never got into, and apparently everyone else since tickets for saturday were practically being given away on craigslist for it. Sunday had absurd lineup overlaps -- I went primarily for STP and Dylan and had to choose. And the teeny-bop warped tour bands (Taking Back Sunday 2.0, Paramore) were annoying, but then again, they're the only reason my girlfriend came, so, can't please everyone I guess.
I can honestly say I was extremely unpleased with the lineup and with good reason. When I, as an educated concert ticket buyer, know Portishead, Prince and The Verve were doing Coachella; My Bloody Valentine was doing US dates; and Radiohead was doing festival dates within one week of your event, then I cannot in good conscience swallow NIN, Kanye, Jack Johnson, Lil Wayne, and The Offspring amongst your events headliners. I idiotically held off on a Coachella or Lolla trip thinking your event would be close to comparable as far as headliner quality, and I cannot say had I known all the festivals lineups on advance that I would have even considered attending VFest. Next year, I can't say I'll give VFest the benefit of the doubt.
I guess in the end, as well run as Vfest is put together, if you get subpar talent and can't decide whether you're throwing a rock event, an indie event, or a rap event (this whole "cross genre" thing ticks off way more people then it appeals to), Vfest will remain a US festival footnote.