i'm doing friday + sat at APW, and am seriously considering sunday at VFest.
taking amtrak up to APW is a great idea. from newark railway station, they claim to have a direct shuttle/rail to LSP. alternately, it's a short walk from the PATH train. question is, how will you get home? last train back to bmore/dc isn't that late, would require missing some of the radiohead set. you'd need a hotel, or a ride back.
single-day ticket for friday are still available, but i wouldn't wait too long before buying them. saturday single-days sold out the day the went on sale.