Carrierwave is my favorite gem for handling uploads and image thumbnail generation (attachment_fu died of old age and paperclip suffers from hashitis, not a pretty picture)
Anyway our imagebank was still on attachment_fu even though I upgraded to rails3 months ago. We couldn't add images and going through some dirty hacks to resuscitate attachment_fu was too much black magic.
So CarrierWave it was.
But how to stick to attachment_fu's naming convention. CarrierWave has a nice and clean way to migrate from paperclip but none from attachment_fu, because J. Nicklas claims, they're too far a part.
Well here's a little module you can include in your uploader and adapt to your needs.
Any Questions ?