The 5.7 is a fine firearm and pleasant to shoot as long as you have your ears on. The only problem is the cost of feeding the beast. The best ammo you're able to purchase at this time is FN's SS197SR, The low cost alternative made by Federal isn't worth the money! Compare the ballistics of both brands and you'll see why, Federals 40 gr, fmj 1655 fps 243 ft. lbs, FN's 40 gr. V-Max 2034 fps 256 ft. lbs. The cost of the ammo seems to be going up each year and the number of manufacturers aren't... something to keep in mind if you're thinking of spending the money for this FN offering. There was a long period of time a year or so ago when you couldn't find any 5.7 ammo around anywhere, will it happen again? Who knows?
Don't misunderstand me, I really like the pistol and it's potential. It has FN quality throughout it's construction and the accuracy is very acceptable as well. If you can absorb the initial cost and continuing feeding without complaint then you'll be happy with your purchase. As an alternative with similar ballistics you may want to research a .22 mag pistol if you can find one. AMT/Javelin made one some years ago, Kel-tec has one out now, Ruger is rumored to be making one, and there are a few revolvers including short barreled ones available by S&W, Taurus, Ruger, and Charter Arms. Hope this has been of some help. Take Care.