Well, it depends on what you're looking for. "good" as in fast, it's not very fast onboard, regardless of where you are. "Good" as in remaining connected, we've never had much issue with that (albeit - slow).
We just use our laptop while in our room, and had no problems connecting, and staying connected. We've found the fastest (not as fast as home, but fast for being onboard) connections were typically when we were online after the late show, or early, early in the morning. Anytime during the daytime, you competing with everyone else who wants to use the internet.