If you want the frankly sluggish Lotus Notes to perform a bit better on your mac then one thing you could try is adding the following line to your Preferences.
UseBasicNotes=1
As settings go this is about as self explanatory as they come, this will tell Notes to use a slightly cut down version of itself. There is nothing I personally haven't been able to do since switching this setting on and the program is more responsive and has better loading and closing times as a result.
The preferences file is called Notes Preferences and can be found in /Users/{you}/Library/Preferences/
Thanks to @geoffhiggins for the tip.
