The Pentax K-x won the best travel gadget of 2009 in Times Magazine and won the best beginner DSLR of 2009 in Times UK.
The Pentax K-x contains a APS-C sensor with high ISO image quality that rivals that of full frames from the Sony A900 and A850.
Pentax has used the exact same mount since early 1970's, the K-mount. This allows EVERY single lens made in the K-mount since the 70's to be able to fit and work with the Pentax K-x. There are also M42 lens mounts for the K-mount that allows every single lens ever made for Pentax SLR and DSLR system to work with the K-x. The Nikon does not boast this capability.
The Pentax K-x has a built-in image stabilization system that helps prevent blurring photos, this allows all K-mount lenses that fit the K-x to be image stabilized, even old ones from the 1970's. The Nikon D5000 does NOT have this feature and you will have to buy more expensive lenses with vibration reduction.
The Pentax K-x has a built-in screw-drive autofocusing motor, the D5000 does not. The K-x will be able to autofocus on lenses that do not have a built-in focusing motor. This allows every single autofocus lens new and old that has the K-mount to work on the K-x. The D5000 does NOT have a built-in screwdrive and cannot autofocus on most third party lenses from Sigma, Tamron, and Tokina. You will have to be the more expensive built-in autofocus motor lenses to autofocus with the D5000.
The Pentax all throughout it's lifespan has a rich history of making superb prime lenses. The Pentax FA 31 F/1.8 Limited lenses is known to be one of the sharpest lens ever made. The Pentax FA 50 F/1.4 lens is known to be one of the most affordable high quality optical lenses in the autofocus 50/1.4. With the FA 31 F/1.8, FA 43 F/1.9, and FA 77 F/1.8 Limited series lenses, there is no going wrong with Pentax lenses.
The Pentax K-x has been reviewed by many websites all over the web and has been praised by it's ability to boast so much in such little price and in such a little body. It also comes in red, white, and blue colors.
Do I need to say more? Any more facts need to be added? I already added up supporting sentences. While everybody who says Nikon this or Nikon that will just say Nikon because Nikon is Nikon. The fact is I say Pentax because Pentax has THIS and it has THAT which others don't have. Now which are you going to choose? Nikon because someone tells you that it's Nikon or are you going to choose what's BEST FOR YOU? Pentax.
Do you need know more? Do you need me to feed you more? Go to http://www.pentaxforums.com/forums/ and I will show you more like you never know more because all there is to know is no more.