I agree, but I'd like to expand on it a bit:
How about being able to convert all maps. For example, if there was a function to change the map type, and it happens that there are American style buildings on the map, they all get removed during the conversion process.
Still can't get over the fact that we can't combine sets though Yeah I know, I'm whining.
For both issues - converting maps and using both sets on one map - can be solved. You can find the informations all in this forum. Its a bit of word - but it works.