Well, it has been a bit of a wait, but now Best Camera has been updated and supports the iPhone 4 with multi-tasking, new filters, a customizable filter interface and sharing options.
What's new
• iOS 4.0 compatible, including multi-tasking
• Supports max resolution of iPhone 4 camera
• Customize dock by organizing your filters
• Partial (50%) versions of filters (in "Settings")
• Supports iPhone 4 Retina display
• Shortened bestc.am link now appears at the end of tweets
• Various bug fixes
Version 1.3/$2.99/Download here