For instance, I would normally write the following sentence:
Many were the dangers arrayed against me, but I had no fear.
Is it grammatically incorrect to write instead:
Many were the dangers arrayed against me, and I had no fear.
I noticed this whilst speaking with a co-worker, and found he extremely rarely used the conjunction 'but', favoring 'and' instead. Though it sounds strange to me, I cannot find anything to say this is grammatically incorrect.