I agree with the other customer reviews about the tiny screen size -- the active display area is about 11mm tall x 21mm wide! Unlike LCD character displays, this device just displays dots, so you need a font table to be able to display individual characters. I used a readily available 5x7 font table to produce 8 rows of 16 characters each. An individual character ends up being about 4pt.
The module VCC pin can be powered from 3.3v or 5.0v (there is an on-board regulator), but the SCL and SDA pins are NOT 5v tolerant and must be pulled up to 3.3v.
No documentation comes with the device, so you have to dig around to figure it out (the customer reviews are helpful). Otherwise I would have given it 5 star.