I have a bit of experience with the FNX 45 Tactical. There are some very cool things about these guns, But there are some major problems as well. First, there is a mag release issue where the mag release button contacts the mag when pressed and wont allow it to drop free. Second, there is another mag release issue, where mags get hung up on the mag release button while INSERTING the mags. Thirdly, there is ANOTHER MAG RELEASE ISSUE, For some reason magazines do not want to drop freely due to being "sticky" in the mag well.
The first and second issue are fairly easily fixed with a file or dremel, and a bit of time. The third is more elusive. There seem to be several possible contributors, but it seems to be more common in the FDE models. I think there is a problem with the polymer personally. Its a little soft and if you grip the gun hard, it torques the magwell and forces contact with the magazine. It seems to react to temp and humidity. I had to send mine back to get it looked at. They did some filing inside the magwell and sent it back to me. It worked much better initially, but the stickiness has crept back.
The biggest problem is that FN KNOWS about these problems(and has for a couple years now) but does its best to ignore them and/or sweep them under the rug. FN customer service has quite the reputation in the states. Spend some time on fnforum dot net and you will see that there is plenty of other users that have had issues.
That being said, I still love it. Just be careful where you buy, and try to test that the mags drop free before buying, or make sure the store has good customer service policies(Wanstalls is Fantastic).