Would a US rate rise really be such a big deal?

The Fed’s FOMC statement is out later this week, at 4am AEST Thursday morning. Fed funds futures are now pricing only a 12% chance of a hike, well shy of the 60% benchmark the Fed has unofficially observed when making rate rise decisions over the last 22 years. Nevertheless, there has been some market speculation on the Fed breaking with convention and announcing a rate rise, and this has caused significant market volatility. However, if we do actually see a US rate rise, from 0.5% to the 'lofty heights' of 0.75% ... would that really be such a big deal?