Mac OS X 10.7 Lion: Hands On (Retail App Store version installed on a PC)
Latest retail DVD version of Mac OS X Lion running on a PC laptop (10.7.3), specifications:
Intel Core 2 Duo @ 2.67 GHz
Nvidia GeForce 9400M G (256MB of DDR3 SDRAM)
4 GB of RAM (2x2 GB 1067 MHz DDR3)
Coincidentally, this PC laptop has very similar specifications to the mid-2009 15-inch MacBook Pro (the one that costs a cool $2000).
http://support.apple.com/kb/SP544
Mid-2009 15" MBP:
Intel Core 2 Duo @ 2.53 GHz
Nvidia GeForce 9400M G (256MB of DDR3 SDRAM)
4 GB of RAM (2x2 GB 1067 MHz DDR3)