I recently purchased PS CS5 extended.
I qualify for educational pricing and this must be one of the biggest bargains ever.
The educational price is 70% off the retail price and the version you receive is the full version, not crippled education edition.
If you qualify for this discount then go for it, you'd be mad not to!
I run it on my "photo" laptop, an AMD quad core Phenom with 8Gb ram and AMD Radeon graphic card.
This laptop easily runs PS and LR and together with a Wacom Bamboo pen and tablet makes using them a joy. A second monitor provides the final touch of luxury to my setup.
some of the money saved on the purchase of PS meant that I bought a couple of PS books by Martin Evening, I can recommend these as very informative indeed.