if by worthwhile do you mean "published"?
Your completed novel - which is, any way you cut it, a large accomplishment itself - is worthwhile by virtue of being a story that any one reader can enjoy, whether its published or not. You can enjoy it, your kids can enjoy it, family and friends. That is idealistic, yes. That's not the answer you were looking for but there is some truth in it ..
But consider, there are a lot of agents out there. A lot. It requires research and patience and rejections. If your a new writer and you are not delivering A+ material, many agents won't accept a B or B+. They *should*, because I bet some of the worlds best writers started out at B students. Chances are they improved their craft, revised until their eyes bled and even then it took working with an agent who'd take a chance on an unpublished author. Its rare these days I think. But they are out there.
You can increase your chances of positive feedback by, I think, being very selective on who you target to query. I've learned its not about simply finding an agent who "represents your genre" therefore you should query them. Think - do they seem like the type of target audience for your book? A book about second chances for a late in life divorcee might not resonate with a 23 year old agent; just as a book geared for Gen Y'ers might not resonate with an agent who has been in the business for 40 years. Of course it comes down to individual taste and there are always exceptions, but sometimes it also comes down to logic. Your chances of getting a full MS request are likely to increase if you pick a small agency than a large one. The large ones are overburdened and I've even heard agents in person whine that their inboxes are so clogged with queries that they just start deleting them. That is NOT the agent you want, though they probably get the most face time on the web and conferences.
Your chances for representation, as an unpublished author, will increase if you start small. These super agents with their awesome blogs? They're great and all (esp Nathan!) but I guarantee they're not going to take time to nurture a B or B+ writer even if they have all the potential in the world. Even if they have that "certain something" despite a transcript that needs work. There are agents that don't have the patience for that, they are not going out on limbs. Sad but true, and it's likely because they have 1) rare A+ exceptions debut authors, 2) Lauren Conrad BS authors and 3) a huge current client list. Why dedicate time to helping guide a talented newbie writer when they have others who make it EASY for them? Sure its the professional, rewarding and honorable thing to do. It's probably why they went into the business in the first place. But the sad truth is they don't have to. They're not hurting for work.
Query widely but wisely. There are many out there, consider branching out of NYC. Observe Publishers Marketplace carefully. Ignore the biggies. Start small. Even if you get rejected you may get some feedback along the way that you really really need. That's worth so much more than "Dear Author" standard rejection forms from Hot Shot big agents? Don't you think?
It only takes ONE. Even if it takes you a few dozen shots, won't it be worth it? Whatever you do - keeping going and remember its never ever personal.