While I am relatively new here, and challenged by Longtooth's report on his new gun thread, I thought I would write a range report on a new purchase. I picked up a Beretta PX4 and though I am partial to Beretta’s and particularly the recently demised Cougar, I will try to be as objective as possible.
For those that do not know, the PX4, I feel, was created by Beretta to compete with Glock and other polymer service guns. The PX4 is to ultimately be offered in DA/SA (F), Constant Action (C), DA/SA with decocker only (G), and DAO (D) triggers (currently DA/SA or F type is the only one available, I think). It is also to be offered in 9mm, .40 S&W, 357 Sig and .45 ACP (currently just in 9mm and .40). Beretta is rumored to be planning a mid-size and/or compact version to complement the full size (4� Barrel) PX4.
The pistol caliber carbine, CX4, can be had to accept the same magazines as the PX4 Pistol.
The one I purchased is a full size 9mm in DA/SA PX4 Storm. The gun has replaceable and different size magazine buttons and back straps, but mine came with medium appendages only. After a quick call to Beretta’s PX4 fulfillment hot line at 888-268-3265, the small and large mag buttons and back straps are on the way at no charge. I fully expect to start seeing pink and blue plastic back straps on sale at mall kiosks everywhere.

The gun came with three 17 round magazines (though most stores only have the 2-Mag box). From what I have determined (empirically), the back strap and entire trigger assembly are easy to remove and replace. Ultimately, one will be able to replace the trigger assembly with whatever action he desires and configure the back strap and magazine button to fit his or her hand size. You can also replace the decocker and slide catch with slim line versions that should make the gun more concealable.
Well that was a little long, but here is a picture showing the back strap and action removed: (and yes, I took the thing apart before ever making it to the range).

The locking system, like the Beretta Cougar, uses a direct barrel to slide lock that rotates the barrel during unlock/recoil. This allows for a lower barrel axis and thus lower perceived recoil. If you've ever shot a Cougar, you'll know what I'm talking about. You .45 guys should try a Cougar 8045 if you ever get the opportunity. You get more push and less muzzle flip with the rotating barrel. In the picture above (although hard to see) you can see the locking block lug that fits to an angled slot in the bottom of the barrel to cause rotation of the barrel.
Picture of the PX4 Storm:

Now for the range report:
Fired 100 rounds of Magtech 115gr round ball 9mm, 50 rounds of Winchester White Box 115gr 9mm, and 20 Rounds of Federal 124gr Hydra Shoks. Zero Failures of any kind (guess I got it back together correctly
I took the time to disassemble the slide and coat the barrel a couple of times with Militech while the barrel was warm. I find this makes furture cleanings easier and it is suppose to turn into a dry permanent lubricant for the barrel. Do you guys do this? I'm curious.
As to the 17 round magazines, all I can say is Ouch!

I plan to make this my nightstand gun. It has luminous sights and as soon as night sights for this gun hit the market, I’ll get some installed. I hope this doesn’t sound too much like a commercial for Beretta, but I think I will enjoy the PX4 Storm. When they come out the the 357sig, I may pick up an extra slide and barrel in that caliber. I know, I know... this was way too long of a post.
-JohnC