Best adventures for 4e: Wrath of the River King, Demon Queen's Enclave, and the 2 first adventures for WotBS (Scouring of Gate Pass and the Indomitable Fire Forest of Innenotdar. I also like DCC58 a lot (The Forgotten Portal). Looking the way 4e War of the Burning Sky is heading, I would definitely consider that if you want to buy a campaign.