Hi there,
First off, the W is sometimes used because although the upper case Greek letter 'omega' looks like an upside down horse shoe, the lower case Greek letter 'omega' looks almost like a lower case English w.
Second, the design of the line driven LED is partly about powering the LED during normal operation and partly about protecting it against transients that might come about on a typical power mains line. To get both and keep the power consumption down to below 1/2 watt it's a good idea to use a 220 ohm resistor for transient suppression along with a zener rather than a higher value resistor which might consume 1w all by itself during normal operation.
Here is a circuit i designed many years ago and recently updated it for 230vac operation. You'll note there are more parts than you normally see in a circuit like that, and that is to accomplish all goals while keeping power under 1/2 watt.
The 120vac version was built and tested for about a year or two of constant operation. The circuit should last quite a while without any problems.
It's not a bad idea to use a 500v capacitor for 230vac operation.