I had about a 25% failure rate when I bought like 25 back in 5/2003. The real cheap sylvania ones, as I recall, failed the fastest, some within 6 months.
Most of the GE/Westinghouse ones I got then are still in use, and I've had a few of them burn out in the past 2 years.. at least they lived up to their 5 (or was it 7?) year promise.
I have one bulb now in our living room (CFLs there are on 5+ hours each night) that occasionally turns on in a 2-bulb fixture. Like once a week we're just sitting there and it's like a supernova in our living room!