Not only for Transport
The Suica IC card is truly the ultimate IC card which makes transportation so much easier, obviating the need to buy a ticket. However, it does so much more.
Suica can be used for shopping at most convenient stores, all kiosks at stations, and all vending machines at stations. The number of places you can use your suica at is also increasing day by day. Shopping with suica makes hunting through your wallet for change unnecessary and makes life easier.
The Suica can also be connected with your credit card. Once you do that, you don't even have to charge your suica anymore. You also get points for whatever you buy on the card and can trade points in for products and discounts.
A very "deeeep" way I used my suica once was to retrieve cash when I was in desperate need of it. I was ready to take the bus home when I realized I have no cash on me. No credit or debit card and only my suica. I went to the train station to see if I could take cash out of my suica. The station attendant told me that it was impossible,"officially". Noticing how in need I was and feeling sympathetic, the attendant then showed me the "unofficial" trick. What you first do is you purchase a ticket of an amount that you want in cash. Then you return the ticket back into the machine and use the reimburse option to retrieve cash. Use this trick if you find yourself in need of cash!
On visit to Japan, definitely get a Suica!