The new MacBook Pro with the high-definition screen has a name that hardly trips off the tongue, so I'll just refer to it as the Retina. Comparing the new MacBook to my outgoing MacBook is not that indicative, ie it's not a direct comparison to the outgoing version of the MacBook Pro. However, there are links to some below.
I bought my old (mid 2010) MacBook Pro at the wrong stage of the cycle, out of need - just months later it was replaced by quad-core models, and Apple also introduced Thunderbolt, making my 2010 seem redundant almost immediately, and also excluding me from checking out exciting new Thunderbolt devices with their impressive throughput speeds. When my daughter bought a 13-inch MacBook Pro at the end of 2010, it beat my ostensibly much more powerful MacBook Pro on all tests except video. Ouch.
Looks
The new Retina MacBook Pro not only has a new Quad-Core Ivy Bridge CPU running at 2.6GHz and a 1GB Nvidia video card, it has the Retina Display. It also has an SSD instead of a traditional hard drive. Dropping the optical drive bay (you can buy an Apple external optical drive for NZ$120) and the old-school hard drive meant Apple could shave precious area and weight. Despite the power it's just a shade thicker all over than the thickest part of a MacBook Air. The previous MacBook Pro was 24.13mm thick - the Retina is 18.3mm. The previous MacBook Pro was 36.47 centimetres across, and the Retina takes about about half a centimetre off that (35.89cm), and front-to-back the new one drops too: 24.71 compared to 24.94mm. All around it's slightly smaller despite the screen staying at 15.4 inches diagonally. It's also 25% lighter - it's definitely easier to carry, and to get in and out of a laptop bag. Bonus.
As for ports, there's one USB 3 (backwards compatible to 2 and 1) port on each side, plus an SDXC card slot (for reading cards from digital cameras) and a new HDMI port on the right. This will be handy for those who present - just plug it into an existing digital display (ie, a TV) with HDMI. On the left there are also two Thunderbolt ports (no Ethernet, but you can get an adapter for NZ$50), the MagSafe2 charge port (not compatible with older MagSafe cables) and the combined audio in/out.
USB 3 means you don't have to get a fast, but still expensive Thunderbolt drive. Your USB 2 drives will still work, and finally faster USB 3 drives are also available to Mac users.
Apple played around with the internal cooling to make the fan quieter (it doesn't generate a vibration or hum as it's asymmetric) and also to save space, meaning the speakers could be changed. They are incredibly clear: there still isn't enough bass but with the clarity and extra volume, they're a definite improvement.