I've been here almost a year and since December (five months now) I've been making over $100 a month (about $750 total so far). Most people don't tell you their earnings and that is why it is hard to know what to expect. So I've decided to be upfront. You can look at my hub to see what I've done. That isn't a lot of money and I'm not quitting my day job, but it is enough to make me feel like I can continue. Recently, I've discovered the "stats" part of the hubediting tool--was it always there? It is on each hub you write near the "edit" button. It tells you the earning potential for that individual hub--number of $$$ signs-- as well has how long people stay on each hub.
I also went back this week to analyze my hubs a bit as a whole. Here is what I discovered:
Hubs that get to 500 hits tend to take off and almost always have a few hits each week.
All but one of my Hubs that have over 1,000 hits was published before last September (in my first 5 months--over 6 months ago) telling me that it takes a while for Hubs to "mature"
I also looked through the "success stories" that Hubpages posts and noticed that those who showed their overall statistics noted that it was past year one or two that traffic picked up. So I think perservering and continuing to publish Hubs when you aren't making much is really the way to eventually do well.
However, I also think that the other commenters are right that quality is very important. In one of the Hubpage weekly news reports they talked about "flagship Hubs" and I immediately went back and tried to add more "flagship qualities" to my own previously published Hubs (I continue to do this periodically) and I am now being sure that all the Hubs I publish include pictures, video, a poll, and over 1,500 words if possible.
Hope that helps. I'm planning to do a hub on this soon.