It's horrible. I had it real bad for a while. And of course you try to do anything you can think of before calling the dr. I tried all kinds of insoles, different shoes, nothing really helped. But, I finally had to go to a podiatrist. He told me what I had and it could last a while. In the meantime, he gave me a cortisone shot, which wasn't pleasant, in my foot. It helped for a few weeks, but I seemed to be going back every month to get one just to alleviate the pain. Also, got some kind of boot to wear when I'm sleeping or resting that was suppose to stretch the tendon. (don't waste your money)
One evening my wife and I were in Nordstroms and another customer overheard us talking about my foot pain, and said to try these ECCO shoes. First thing I notices, the arch support was real firm and not soft, like I presumed it should be. But I tried them on and it seemed to help a little bit. So, I shelled out $150.00 for a pair that I could work in. They actually really helped and within a month, no more than 2 months, my planter fasciitis was pretty much gone. That was 9 years ago, and now, I only buy ECCO brand. But I usually go on ebay and find them about half the price. Weather it's ECCO or another brand, you need shoes with insoles that are not "cushiony" but hard and firm with good support.

Good luck, I feel for ya, bro!