FM Pro is a bit limited and inflexible, not to mention it's getting a bit long in the tooth. I'd also suggest that you look at
4th Dimension, it seems to be a bit more of a developer tool. FM is brilliant if you're clueless about databases and want to create a simple solution quickly, but you might find yourself hitting brick walls quite quickly if you're coming from something towards the high end of the market.
I'm not really sure what you mean about "importing a spreadsheet", as csv/tab delimited is the standard for importing/exporting spreadsheet data... MS Excel's file format is closed, so there's no way other developers can just import it (although MS SQL or Access might be able to, of course, since they're Microsoft products and can share code with the rest of the Office suite).
HTH.