Last month I purchased an import 1Dx from GetItDigital without issue. They did call me to let me know of their USA model options that cost more, but it was a very polite call and not a hard sell. Actually, it seemed more like a call to make sure that I understood that I was buying gray market and not a USA model.
As for the gray market 1Dx, it came with the menu set for Japanese, which I had to change. There was no warranty card (as expected). The power cord for the charger was a USA cord. I was prepared for a foreign cord. I also had no problem registering the serial number on Canon's website.
In January, I ordered an 18-135 STM zoom as a gift from GetItDigital. I think this was a USA market "white box" lens that was separated from a kit.
When I ordered the 1Dx, I did notice that they advertised USA model 5D3's at a decent price. So, not everything they sell is gray market.
My confidence in GetItDigital first came from CanonPriceWatch.com, which lists them. Plus, this forum has had other posters post positive reviews and I haven't seen a negative one.
I would order from them again.