I upgraded my mabcbook pro 2011 from HDD (320 GB) to SSH( Samsung Evo 650 500 GB), the result has been amazing. Here are the before and after speeds.
There is jump form 42MB/sec to 500 MB/sec. Overall the system boots fasters, launches programs faster and wakes up from boot a lot faster.
Note that if you connect your SSD via USB, you will get slow speed, that is 30MB/sec which is USB2 max limit.