Pentium U5600 is even slower than the ULV i3s; that'd be a very nice improvement on a netbook for many people doing basic browsing, office, etc. Costs about the same as a used X201, although it's new surplus rather than used, lighter and will have a better battery life. For small machines at this end of the budget, there is no obvious win, just tradeoffs to make.

Refurb with the i7 costs about the same as the Pentium does new surplus:
http://www.ebay.com/itm/Acer-Aspire-...item257252fdd7
but for many workloads will be twice as fast when plugged in given that it's got turbo to 2.53ghz vs. a fixed clock speed of 1.33ghz.