Now i know guinea pigs are the most awesome pet! but thats the point are theyre any downsides too them? i know theyre a bit of maintenance and can stink (which is poor on the owners part) are theyre any downsides?

I've got two guinea pigs, and as long as あなた regularly clean out the hutch(completely once a week, and pick up poopies every day) and they have the correct healthy diet, あなた won't get any bad smell. My two piggies live in an inside two storey hutch and they don't smell at all :)
I can't find any downside with them, the only thing is that you'll need two, because otherwise they get very lonely and depressed. They need a big cage/hutch aswell for plenty of exercise. But that's about it :) hope this helps