Lots of problems reported with only 8gb of RAM. The integrated graphics use 1.5gb of system memory, which does not leave much for anything else. When you run out of memory, virtual memory will do a lot of swapping to the SSD. Since the SSD is so fast, that might not be a big issue in and of itself, but constant disk access generates a lot of heat, which can cause the processor to slow down. IMO you should get at least 16gb.
Get a refurb from Apple's site, that will save you about 15%. They have all different configurations but they sell very quickly, so you need to check constantly and buy the one you want when it appears. Took me over a month, but I got exactly what I wanted and saved a lot.