Novice help: Should I upgrade Snow Leopard to Mt Lion?

To the readers:

I have a imac OS X 10.6.8 version, snow leopard. What I basically do is e-mail, some shopping, store photos, use Itunes, basic stuff. I have an ipad 1, iphone4s, and ipod nano. Not sure if these all need better software? If it matters? I have no issues whatsoever with any items.....

I don't have podcasts, or watch movies through itunes. Just music, and it stores pictures. I have icloud and my products sync, but I don't know details. Right now I have some time to learn so I'm doing so. ( I haven't used the Nano in probably 1.5 yrs or so....saving it for my son when he's old enough)

Is an upgrade something I should do or leave things status quo?

Thank you ( :

Thank you. I was hoping that Leopard would be sufficient security-wise so good to know upgrade is optional. Thanks ( :