I would suggest that you find an agent that you are comfortable working with and work with that agent. You want someone working in your best interest.
The listing agent only represnts the interest of the seller, leaving you with no representation. Are you sure the property isn't overpriced, and that your "lowball" offer isn't actually too high? If you are relying on Zillow or Realty Trac to get home values, you definitely need an agent representing you!
Hiring an agent such as myself costs you nothing and will probably save you a lot in the long run.
David Barr, Broker
But if it's just a listing agent, you have no further obligations to work with that agent on any property at any point in the future.
And Debbie's point in good: There's no advantage, as a buyer, in dealing directly with a listing agent. The commission paid by the seller will be the same. And the agent will still be representing the seller, not you.
I am just curious if you are working with the listing agent and your "low ball offer" in the hope that you will have some kind of an "inside track" on the property??
If so......you might want to rethink your strategy.
I agree with Patrick - find an agent you feel comfortable with, and work with him or her on finding a home. They, in turn, will be working for you and developing a rapport which will help you more in the long run then moving from listing agent to listing agent.
Good luck with your offer and future home search!