The west side of Jamestown is not a harbor. A harbor is supposed to offer a respite from wind, waves and wakes. Jamestown does none of these. The constant tossing of the boat never stopped. In fact, in the early hours of the night, it sounded like something was trying to tear the boat apart. Needless to say, we didn't get any sleep.
The Conanicut Marine was a friendly place. They run a tight ship which we witnessed when someone came and moved a mooring ball they felt was too close to us. The launch service is essential because the waves makes it almost dangerous to try and use your own tender. They are quick and competent when ferrying people around.
I would recommend this location only if there is no wind and you don't mind being tossed around by wakes of large vessels travelling the busy waters of Newport.