Should I delete LIMEWIRE?

I have used limewire for about a year now and the only different thing that has happened is that my computer is running slower yet i don't know if its because of limewire. I heard limewire is dangerous why is this said? Do you think i should delete it? What other program can i use instead of limewire that IS safe and fast. I have Ares but i think it sucks so what can i use and what are the disadvantages?