I would definately speak to the Broker or office manager to see if the issues can be resolved. Most times dissatisfaction is caused by lack of communication and before emotions take over it may be best to ensure that both parties had a full understanding of what was expected both in actions and timing.
There is no better way to sell a home than using a real estate professional, but you need to have confidence in them to do their job to the best of their ability.
All of the professionals that answered have responded with good advise, and i hope we have helped somewhat.

Dan - In order to get out of your listing agreement, you will need to have a valid reason, i.e. marketing plan is not being executed, agent not returning your calls, agent not cooperating with other MLS brokers. If that does not work, ask the office broker to speak to the LIBOR zone chairperson for Queens.

The biggest issues are almost always unmet expectations.
What did you agree to?
What did they agree to?
I would define where they are failing to perform, asking for a meeting with the Realtor, if that fails, with the broker.

In most cases (but not all) the seller thinks their listing is worth more that it really is. It is a shame that some REaltors are unable to communicate in a way that the sellers undertand the dynamics.
A listing has a short shelf life. 10-12 showings in 2 weeks should equal an offer. if not, lower the price.

If there are more complex issues (communication, not performing as promised) then address those. Realtors do not have any control of the market. If your home is over-priced, what you paid, how much you owe, how much you need to net...we have no control over that.

Gail answered well. Talk to the broker.

The first step is to speak to the agent's manager/broker to see if the problems can be fixed. If that doesn't help, perhaps someone else in their office can work the marketing for you.

I don't know what kind of contract you signed, but at some point, discuss with your attorney.

If you are not happy with the current agent because the property isn't selling, look first to the pricing and then to the marketing...