This might be my imagination but I've been downloading some dock icons etc a few things here and there and it feels like my MBP is slower...im not sure if it is but is there a way I can check?
Hmm... If things are feeling sluggish then open Activity Monitor in the Utilities folder and check for any process that's using a lot of your CPU or RAM. Remember to select All Processes from the drop down menu, not just My Processes.