I have to agree with GodBen's assessment of 'Tuvix.' For me, it was somewhat thought provoking and ethically interesting, but ultimately felt incomplete, which, coupled with my irritation with the Tuvix character, has not left this a favorite of mine.
The other big thing that bothered me about the episode was the IMO overly-technobabbly notion that two people could be fused via transporter, and then somehow successfully de-integrated. It bent my suspension of disbelief almost to the breaking point.
I think I'd have found the episode more interesting if somehow Tuvok's katra had been accidentally (or even out of necessity, ala 'The Search for Spock') transferred into Neelix's body, with Tuvok's body theoretically terminally wounded. Not only does Tuvok's katra somehow bond with Neelix to produce a new 'hybrid' persona, but Tuvok's body is able to be recovered, and the 'new persona' which would call itself Tuvix, would argue to stay as it is. I think this type of explanation would have had greater resonance with what it seemed the epiosde was trying to do.