Website is Loading Slow
You have two Caching methods in MashShare. The one is the default Async Cache Refresh method and the other one is the legacy method Refresh While Loading.
If you are using the share method Refresh While Loading in Settings->General Settings it's possible that you experience initially slower page loading from time to time.
When there are no share counts (if it is running first time or Mashshare cache is purged), it is expected to have slower page loads. That's because if there is no cache, then plugin checks for share counts and the results are cached.This operation costs a little page loading time. Once the results are cached, it doesn't check share counts any further until the next cache's expiration time and the page load will be as fast as it was before without any noticeable delay.
Once counts are cached, the pages are loaded with nearly no delay and performance effects.
If you do want to get rid of the initial extra loading time try to switch first the async caching method Async Cache Refresh which never increases the loading time for your visitors.
Don't Take Our Word for It, Test It Yourself
Open one newly created page or post and you'll notice there is a small delay while loading the page. (shouldn't be more than 1 second).
Open / refresh the same page again and you'll notice the page is loaded faster, without extra delay.
Pages Still Loading Slow or There is a Performance Impact?
If you still experience difficulties related to slow loading pages or performance impact on your website, disable the share count from Mashshare settings and check it again to see if the reason is Mashshare or not.