I'm an aging hippy fearful for the world and an early adopter of LED lighting and I like it 8)
If you want a single light in the middle of a room then they still have a long way to go as LED lighting lends itself more to spot and ornamental lighting.
If you use several to light a room then they do a dam good job. Interestingly, due to the limited viewing angle of a single LED I have found with the LED lights I have bought, the smaller the room the more you need
When I first started using LED lights everyone was quoting (and exaggerating) light output differently so making it difficult to decide how an LED light stacked up against traditional lighting. Thankfully, now, there are sites like this
http://www.rapidtables.com/calc/light/how-lumen-to-watt.htm but as a rule a 1w LED is roughly equivalent to a 10w incandescent light.
As other have mentioned early mains LED's did suffer from a delay in starting but all the ones I have bought in the last year are instant start.
Are they really cheaper and more environmentally friendly?
That depends. From my experience be careful of the really cheap Chinese ones as they don't last anywhere near the 25-50K hours LED's are supposed too, 16 hours in some cases
To be fair and because everything is made in China these days
they were replaced very quickly and I kept the faulty ones which meant I have spare LED's for when others fail.
How safe are LED lightsRecently I read this article
http://www.sott.net/article/261790-LED-lights-may-damage-eyes-researcher-says which maybe of interest to others