Update for 2019:
Osram/Sylvania bulbs continue to have some problems as repeaters. Hue bulbs are fine acting as repeaters for each other when connected to a hue bridge, but have the same problems as the Sylvania when connected directly to the smartthings hub.
The Cree bulbs don’t have the problems repeating, but beginning in the fall of 2018 there’s some crazy issue with a firmware update which can cause them just to come randomly on and off. Much discussion in the forums on this.
On the other hand, lots of good reports on the IKEA Tradfri bulbs once they are updated to the firmware released In mid 2018. They appear to be reliable not only for the typical zigbee device, but even for the Xioami sensors which have trouble staying connected with many other repeaters.