Yeah, most Logitech software really lag computers. They should really optimize them somehow. As for an alternative software that will set macro keys for your mouse, I have not personally used any but here are some suggestions that you might want to try out:
AutoHotkey -
http://fileforum.betanews.com/detail...y/1088127602/1
AutoIt -
http://fileforum.betanews.com/detail/AutoIt/968271279/1
X-Mouse Button Control (32-bit) 1.28 -
http://fileforum.betanews.com/detail...t/1145607067/1