I was sure a project of mine was doomed: though once popular, it was imperfect and there was free competition that was the new darling. Ouch. (Oh, and I was bored with it.) I actually tried to abandon it - scuttle it. Today, it's still making money (a $6,000 sale this month), with almost no work from me, while I concentrate on a new, non-boring project. My experience: feelings of discouragement are not always accurate.
Especially if nearing a scary moment-of-truth release date.
You aren't a slave to the project - talk to your partner, negotiate an exit for yourself (with an option to stay).
I was actually an art major and one thing that I learned very quickly was that the last person to appreciate or even understand a work of art was the artist himself.
It's often very difficult to see the value in something you made simply because you were able to make it. Truly take a step back and look at the problem solved, not just the solution. I am sure you will see great value.
It's funny. The other day I recommended a friend signup for WuFoo as a tool for some feedback he wanted from customers. He was blown away by it! A basic form is something that many YCers probably take for granted, but since he had no comprehension of such a task and was able to complete the part he feared the most so quickly and easily, the benefit to him was colossal.
I also agree that you need to communicate your feelings to your partner. Maybe not so much that you think it's a waste of time, but try to understand his excitement; see if it's grounded.
Cheers