While the XD is a fine firearm at the present time it leaves much to be desired from a competition (IDPA, USPSA) standpoint due to the lack of spare parts.
http://en.wikipedia.org/wiki/Springfield_Armory_XD
Pros
The XD can be field stripped easily and quickly with no tools.
Springfield Armory promises a lifetime guarantee with every XD pistol.
The XD series has only been on the market for a few years, so shooters are unable to judge its long-term track record, but the line has already
established a reputation for bombproof reliability. One so-called 'Torture Test' was conducted (see external link below) in which an XD-9 was run over with a truck, frozen in a block of ice, caked with sand, and even stripped and degreased, firing nearly 20,000 rounds without a single malfunction in the process.
The primary aspect that many first-time XD shooters comment on is the gun's ergonomics. It is considered to have a very solid, stable feel, with a grip that feels extremely comfortable in the hands of even smaller shooters. These types of comments are especially impressive when applied to the XD-45, since grip size has been a major problem for other high-capacity .45ACP pistols.
The XD's grip angle is the same as that of a 1911, which tends to make the gun more naturally pointable in the view of most American shooters. Many polymer-framed pistols such as Glocks tend to have a more severe grip angle (wrist is held such that a 1911 syle pistol would be pointed more towards the ground), which has been regarded to be more of an acquired taste.
The sight mounts on XD pistols are essentially the same as sight mounts on the popular line of pistols made by SIG, meaning that there is a large variety of aftermarket sights that can be installed on an XD without modification.
The XD uses a fully supported chamber design which reinforces the rear of the ammunition case. A fully supported chamber reduces the possibility of an ammunition case rupture that could cause injury to the shooter and severely damage the gun. This is an especially important feature for owners who intend to use +P and/or reloaded ammunition.
The sights and trigger of the XD are made of metal instead of plastic
Cons
Though some parts can be purchased through aftermarket suppliers, Springfield Armory refuses to sell some individual XD parts. Springfield Armory's position seems to be that with a lifetime warranty that includes repair work, parts sales are not necessary. This is a major stumbling block for shooters who are involved in competitive pistol activities, because they are unable to keep a small stock of parts on hand for emergencies. People who carry their pistol every day (and thus are unable to ship their gun off for a week while it's being repaired) have also complained about the policy.
As of 2006, there are no aftermarket trigger springs. This means that shooters cannot adjust the trigger pull weight of their XD pistols for competition or personal preference.
Those who have tried installing aftermarket or custom sights on XD's have reported that removing the existing sights can be an extremely difficult process, often requiring the services of a gunsmith.
Pre-2006 versions of the XD were protected with a metal treatment called Burinal™. Some who own pistols with the Burinal™ treatment have reported significant rust problems - especially those who carry the XD against their skin. Fortunately, current versions of the XD are being manufactured with a treatment called Melonite™, which is the same process as the near-legendary Tenifer™ coating used on Glocks.