I have one of these. Excellent digital scale. You don't have to belong to Stamps.com to use it. Just plug it into your computer (USB) and it'll work. Very accurate.
I use stamps.com and its great. You do have to have the disk to install the scale. I know you can work offline and weigh things.....but to print postage you must have their service which is 15.99 a month but you get discounted shipping on First Class, Express, Priority, etc. You can't print First Class and Media Mail from the PO so this is neat. The first two months you get 10.00 in free postage if you sign up. Anyway..just some information for you Listians.
I use Stamps.com for my mailing needs and you should try it out. Use this code to sign up, C-9R8R-H89, and you will get a $100 offer which includes a digital scale and $45 in postage.