We are one of the earliest users of Manifold in India, but I have not seen many copies anywhere so far. Most of the users are government and private agencies still rely on ARC family and it is hard to break the monopoly due to "institutional benefits" they offer as well as everyone asking for ARC format outputs. Also illegal copies are available everywhere. We have tried to promote Manifold due to simplicity in use, single map file format, and on the fly projection added to the price advantage ( ARCGIS costs anywhere between 20 times that of Manfold, but many institutional clients seem to "like" it that way). After seeing clients interested in bigger budgets for obvious reasons, I find it is going to take time.
We have used it to build a multi-hazard risk atlas, as input to a variety of modeling exercises and also have developed a IMS on asp.net with over 200 maps, but it is hard uphill task with other costlier software vendors having gtheir way in this system. Art Lembos videos are used to train freshers in a matter of days, and it is easy to get going in Manfold. I have lost my bearings in new ARC family products now, since I donot find use for it, expcet for some very specific tasks.
I would say it is an ideal package for small and medium municipalities, which are forced to improve their performance, but Manifold may require different market strategies to address that clientele.