Most of the comments by drivers are that it's not busy enough. You get a trip to one side of town and then you are left sitting there without another fare. They then have to either go home or drive to another part of town to try and guess where more fares will come from. This will likely be solved with more customers, and that's where my comment about Uber subsidizing more rides came from.
EDIT - A lot of the drivers also appear to be out of work to decided to drive for Uber to make some spare cash (the drop in oil prices hurt Calgarians). So they didn't have a boss before Uber, they were unemployed. So I think they appreciate the extra income, but it's not as much as they hoped.
In the bay area I've had mixed experiences. Drivers in the city seem to be interested in a chat. In the south bay I've taken to wearing earphones just before getting on so I don't have to hear how evil Uber is.
I always make small talk and usually ask how their experience has been. I always get a "meh" response. No driver has ever said it's awesome, and no one has said it's terrible (those drivers are likely not taking fares anymore). I can see why drivers don't remain on the platform. If you take a short break for whatever reason, you likely have very little motivation to pick up again. It doesn't seem like it's life changing for any driver in my city (one driver did say it was good for him, but he was a realtor who would hand out his business card).
I think this shows why Uber needs to subsidize so many rides when first starting out. They need to provide their drivers with tons of business, otherwise the two sided marketplace doesn't get solved.