It is an achievement. As to whether or not it is a "grand" acheivement is certainly going to be viewed differently by different people.
I does represent a lot of time and work, and in many cases, research. For those new to writing, it may well represent a grand achievement; to others, accustomed to writing all the time, they may toss of 100 articles in a month with little or no extra effort. (See the forums for the Hub Challengers 100 Hubs in 30 and 60 days challenges).
I'm finding it challenge enough just to get through 30-in-30; and I'm approaching 200 hubs. I'm pleased with myself for reaching that milestone, and I'll pause to pat myself on the back when I do hit 200--but I have greater goals, so no, for me, my 'grand achievement' will be reaching my final goal, regardless of how many hubs I've written.