lol, got worried myself when i chose I2C.
Per my last comment, looks like Spark were doing a lot of upgrade stuff today, which could explain IDE taking approx 45 seconds to download to core.
Back to SSD1306, (I have a Adafruit 3.3v/5v Device)
My core is mounted in shield, so i have 3.3v or 5v available for display.
As soon as i read your comment, i was checking into pin assignment.
Yes, i was using RX/TX, but have now switched to D0 and D1 (so 3 & 5 on shield shield)
either way i get nothing, trying to use I2C.
cant get adafruit splash screen, have tried rx/tx pins before switching to shield shield 3 & 5, but no result.
no errors reported anywhere in IDE .
oh the fun getting something working, lol
ps, did find one thing. your Github file for Adafruit_SSD1306.h has a default display address which is not consistent.