I mostly deal with ISS and I love them! They actually have scheduled paydays, every 2nd Friday, so you know when you're going to get paid for the jobs you do for them. I wish they had more jobs around where I live. I only get jobs from 2 companies...ISS and Scheduler at 360 and you have NO idea at all when you're going to get paid back by them... somewhere around a month, and the jobs they have usually involves putting out a decent amount of $$$
I have never looked at the iSS spreadsheet... I have created my own for tracking shops, expenses, payments, etc. It's pretty simple to set up with Excel. Most of my shops are not through iSS, so I needed a document that would handle them. Were I just to us iSS, I'd likely be happy with what is offered online (the "assigned shops" tab and the "payments" tab).