Tell me about HD cable service please

[AlphaDog]

My digital box got fried yesterday when the power came back on after being off for 13 hours, and Comcast will be coming out Monday to replace it. It's a digital cable box, but it is not the one for high def. The TV is HDTV ready. Do I want to upgrade? What, if any, are the benefits to going to the high definition? I think it's an extra $5 a month, which wouldn't break the piggy bank, but I won't bother unless I'd notice really cool differences.