simple Kudos thread!
I'm having the same issue as jgainsborough.
I formatted a 4GB SDHC as FAT32, extracted the zip to it, inserted into powered-off BBB, held down USER/BOOT applied power, and waited. Never saw any lights other than the power light. Have tried many times, holding down USER/BOOT for as long as 30 seconds.
Have tried with USB and with power supply. Same behavior. Board boots runs fine from internal memory.