I finally got there. 50 uploads. It took quite a while (almost a year in fact), and at a certain point I'd given up hope altogether, but I got there.
The most important thing, though, is not reaching the milestone, it's the path you travel on. For me, it meant learning quite a lot about photography (I was a beginner when I uploaded the first shots), and quite a lot about this "microstock" business, with its pitfalls and (mostly) unwritten rules.
In the meantime, I switched cameras (out went the Fuji S9600, in came a Canon 400D), invested in a rather sizeable amount of objectives, and most importantly had quite a lot of fun taking pictures, regardless of their "sellability" (if you're interested in my "non-stock" stuff, it's on Flickr).
Interestingly enough, image #1 and image #50 come from the same photo session, a walk through the vineyards near Lausanne, in Switzerland. Things go in circles sometimes...