Well for basic usage "web surfing, email, word processing" any of the processors should be fine. The core2 will do a lot better with "photo work, video editing, gaming, etc. I personally just purchased the same Lenovo @ Officedepot with the Intel Core 2 Duo. Its on sale for $699 with a $130 mail in rebate = $569 which imo is a steal. Battery life is not stellar but average. I get about 2 1/2 - 3hrs doing basic things with the brightness a few notches down. Thats with wifi on.
I say go for it. Its a great machine! Good luck!
After a couple of days of online reading, I have decided to buy a the Lenovo IdeaPad Y510 hoping for some IBM reliability within my price range. The Y510 comes in several different configurations some sporting the Pentium Dual Core 1.6G T2330 and the Core 2 Duo 1.66G T5450(or the larger 1.83G). My question is this - what sort of performance difference will I actually see between the dual core Pentium and the core 2 duo? I am concerned with both speed and battery life. I just want to know if the core 2 duo is worth the extra couple of hundred dollars.