When I hit the switch, there is a fraction of a second lag before they all come on in unison, but they don't need to warm up like CFLs. They start out bright, and I doubt they are impacted by a cold room like fluorescents are.
For me, it's fairly instant-on. There might be like a second of delay before it's bright but often the delay is not noticeable for me. So you might have gotten a defective one. Probably the LED driver circuit not working as it should for yours.
I can't speak to your light, but we have 3 of these bulbs installed in a track-setup on our kitchen ceiling. As far as I'm concerned, there is NO lag. I do have 4 LED bulbs purchased from an unknown vendor (via Grou*pon) that have an absolute lag, so I know what that feels like (it's weird). But these have no discernable lag to us.
Gary, a slight lag in on time seems to be normal for these lamps. Even the Philips AmbientLED I have does the same thing. It doesn't bother me and at least the lamps come on full brightness after the lag. I agree with the other commenters here that the lag is less than a second. Only if its longer than a second for you would I say you have a defective lamp. I hope this helps you! Michael R
I have noticed on certain manufacturers, there can be a second or two delay. They are exterior PAR light buldbs that I bought a year or more ago. These light bulbs come on and if there is a delay I hardly notice or care.