Why do my LED bulbs have such a short lifespan?
I don't know if it's really useful to compare a 120V LED bulb to the stuff you can cobble together from radio shack. First of all the commercial bulbs include a significant amount of circuitry to adjust the voltage, compensate for dimmers, etc. Most bulbs actually accept a wide range of input voltages. And of course with an AC circuit there is no such thing as polarity. Plus the diodes themselves are often quite complicated, mixing various colors and also combining phosphor coatings that are not feasible to do yourself.

But to answer your question about how good they are... I think they're excellent now. I started buying them 5 or 6 years ago when they were $30/each (for high-usage areas only), but the price now is down to about $1/bulb so I don't see why you wouldn't replace every single old-fashioned incandescent at that price. The energy savings will pay for the bulb in only 10 or 20 hours of use.

Also I don't think I've ever had an LED bulb die yet... even using some bulbs in enclosed fixtures even though they're not rated for such usage. (Many bulbs are now, so if you have enclosed fixtures that is something to look for.)