I've got and have extensively shot an FS2000. I think it's an excellent rifle. It's unbelievably short and handy. I don't like the standard forend, so I got rid of it and installed FN's rail system for it. I put a forward grip on it and the thing really handles nicely now. It also looks better, if that matters to you. However, the rail adds a lot of weight to the gun, so it feels pretty front-heavy where it was balanced perfectly before. You'd have to handle it yourself to decide whether that's a big deal to you.
The trigger is mushy and not anywhere near an AR trigger. Again, that might not be an issue for you (isn't for me) but your preference might be different. There are a couple of models out right now, and one comes with the original FN integrated optic. I wouldn't get that one if I were you, because underneath the optic there aren't standard rails. You'll have a problem mounting your own optic if you take the original one off.
Also, mags don't drop-free with the FS, as there is a gasket around the inside of the mag well to keep crap out. You have to grab the mag and positively pull it out. In competition I like a mag that drops free, so if you're going to use it for that, you might want to consider this. If you're not going to compete, it's probably not an issue. You might also be able to take the gasket out.
Regarding the forward ejection, it really works flawlessly. I think I saw a video someone made sometime where they tried to get the thing to jam by putting a lot of cases and dirt in there and shooting upwards and all that stuff. They couldn't do it without getting ridiculous. And really, if you see how the thing works, and how each case is forcefully grabbed by the action and then flung forward into the tube, you'd see why it's unlikely. There's an inspection cover that you can lift and watch everything happening. It's a very nice system that has worked great for me.
I've got just about every 5.56 "battle" rifle out there, and I can say that I like this one a lot, now that I put the rail on the front. If I were only going to have one 5.56 rifle, it wouldn't be this one, but if you like it, then try it out before you buy it. It's an odd little gun, and not everyone's cup of tea. I'm happy to let you try mine if you'd like.
Here is what the rail system looks like. Some people put stubbier grips on the front to make it look more sleek but I like a full grip:
