I have a boring job, so to make the time pass by faster, I listen to quite a few podcasts. I thought I'd share with you some feedback from a listener's perspective. 

Make sure the volume is loud enough.  I usually listen to podcasts when either when I'm at work, at the gym, or on a long car ride.  All of those have background noises I have to deal with. I've have chosen to unsubscribe from a few podcasts because the volume was too low and even if I turn the volume on my iPod to the maximum, I still have trouble hearing it. 

Another issue with volume is to make sure the volume is at the same level for all people on the podcast.  I listen to one podcast with 3 people, but one lady on the show is too quiet, so I have to turn it up in order to hear her, but then if one of the others starts talking I have to quickly turn it down so it doesn't hurt my ears because their volume is too loud compared to her.  Often people want to listen hand-free while they are exercising or doing other things and they don't want to keep reaching for their mp3 player to adjust the volume.  This also goes for music included in the podcast too.  Sometimes the podcast is one volume, but the if they include an intro song or play music as they go to commercial, it's often times louder than the rest of the show, and I have to keep adjusting the volume.

Speaking of commercials, I understand why you want to include them, but I've found if a podcast only breaks for 30 to 60 seconds, I'll just let the commercials play, but anything longer than that I tend to fast forward. Again, please keep the volume consistent because if I'm diving for the iPod to adjust the volume, I'll probably also hit the fast forward button while I'm at it.

Another pet peeve is annoying jingles. Just like commercials, the shorter the better. I'd prefer none at all, but that's just me. If it sounds cheesy, chances are it's more of an annoyance to your listener than it is something clever.

My last tip is keep your introductions short and don’t make the first several minutes the same every time. I get bored real fast when I can pretty much recite the first few minutes by memory because the podcaster says the same thing each and every podcast.

Again these are just my opinions, but I hope this helps anyone who is a podcaster improve their podcast and get more subscribers!