During the transition from a thin to a thicker atmosphere, there will inevitably be a phase when it is not yet warm and wet enough to damp down the dust, but windier than it is now. This would include everything up to about half a bar of CO2 atmosphere.

That would be an unpleasant time. Kim Stanley Robinson, in his telescoped chronology of Terraforming wrote about duststorms and interminable boredome during this period.

In reality, things would be slower, last longer, and be more boring.

A *fully* terraformed Mars will be fine. Just a pity that it will take 10,000 years to get there, but have patience:- "the journey of 10,000 miles begins with a single step"