Us in the trenches will let you know that the expectations are very high, editors are on the lookout for specific books, and querying with something good won’t cut it; you need to go on submission with things that are great.
Yes, agents can help you get your novel into tip top shape, but when we get your manuscript and start reading we don’t know if this is the best you’ve got or whether we can push you. Getting back in touch and suggesting revisions takes time, and we don’t have a lot of it. So never, ever, send out something that is ‘good’. You’ll get some polite passes and praise for your writing, but you’re not going to hook an agent that way and you’re certainly not going to hook an editor that way.
So be prepared for what the market is going to say to you.
You can’t be too market sensitive when you’re writing, but remember how tough it will be so put those extra hours in now to get your work into the best shape.