Even for the MacBook three years ago, it also has a surprising effect when running Mountain Lion. First of all, during one-week use, I rarely encountered the system crash; Secondly, so far i have not encountered any major problems.
Of course, Mountain Lion has compatibility issues with some software, such as Google's Chrome browser, but on the native software of the Mountain Lion, the running speed still satisfied me. Mac tip: rip dvd to mac. I believe in the future the software compatibility issues will be gradually resolved. The new features Apple added in Mountain Lion and native software also have the desired effect.
In general, there is no slack phenomenon when Mountain Lion running in my machine and i can feel it is significantly improved compared to the Lion. Although I encountered some problems several times when using me Machine and screen sharing, but it did not have much impact. Mountain Lion is only a test version, I believe Apple will gradually fix these small problems in the next update.