We really recommend the product, it may have some disadvantages to dropbox but it's very very usable, evolving and we're very happy about it.
I'd also be curious how much maintenance, setup, etc., work you estimate is involved.
Another disadvantage might be that their mobile apps are not free, they are at a more than reasonable price and I don't mind the business model but it could be a little bit uncomfortable, do the employees pay the $1 and then get it back, do you send them as gifts? (Google play doesn't support gifts for example). Not the end of the world but still.
Well, we didn't pay for a Dropbox enterprise account or anything, we always try to minimize costs, that meant that you wither needed to switch between personal and business accounts or use the web interface for one. It also meant that we were constantly overflowing our limits. Dropbox is no offering more than when I last checked, but right now it would be for 22 users €3,168 per year.
I was not so closely involved with the setup but I believe it was pretty straight forward and we've been using with basically no troubles. The software works nicely.
Paid Android apps are not available in most countries so this is why you'll see some released in both markets like this.
Tell the employees to grab it there, and make a donation to ownCloud if that's easier for you.