Actually Dad and I both bought the "Livio" appliance that acts as an internet radio with Pandora specifcs built into the device and the remote (thumbs up/down, skip, channel select, presets, volume and such). With the purchase of the radio you get a modified version of the free app that you can access with a PC. The free version allows 40 hours of listening per week. Many folks may never run into this limit but, with my job and hours, I do ;-) This limit does not apply to the Livio appliance.
I started listening to Pandora (and others) on an old laptop hooked up to a set of powered speakers in the shop. I listen to free Pandora on whatever computer I am using at the time at work and the Livio radio at home. The commercials are not as frequent on the Livio as they are on the PC or at least it seems that way to me.
As to having the same songs too often; this can be a direct result of your seed artists and seed songs. If you have not tried modifying these settings for a given station, give it a try. It took me quite awhile to "tune in" my station that is primarily keyboard artists but I am very happy with it now. I have other stations for Guitar, Metal, Folk Rock, Classical, Chamber, Swing, Blues and so on. Being more specific for a given station leads to a greater array of similar artists/songs but, I do keep a "General" station that is more wide open.