I find emails much easier to deal with when the actual emails are in the list, rather than the conversations - although when displaying the message there's no reason not to show it in the context of the conversation.
I always turn it off, but I think conversation view might be worth it with the following changes:
1. When viewing a conversation, always expand all email and cut quoted text from each email. The fact that quoted text is shown which duplicates email in the same conversation makes for a horrible mess.
2. Use the proper headers (Message-ID, IIRC) to determine which emails belong to the same conversation, rather than the current fuzzy-logic based on the subject and current phase of the moon. At the very least, implement this logic: two separate emails, neither of which are a reply to another email, do NOT belong to the same conversation.
Conversation view is the single worst software feature ever developed for any piece of software ever made.
Boy I wish I could turn it off in the android gmail client.