Roads55 posts a lot of dismissive shit, but without offering reasons why. (This is the same guy who recommended everyone panic and mass withdraw all funds from 5Dimes after the Tony situation)
I've looked online and NitrogenSports has a solid B+ rating from the SBR, which is decent for a book that has only been around 2012 and whose first rating, a B, was in 2014. No major complaints, and they are known for quick, easy payouts.
Until sportsbooks become legalized in more US states, this is fairly legit, yeah.