My company only uses Concur for expenses, not booking, and I love it. I photo my receipts as I go in the app on my phone, match them to my expenses as they import in from my corp card, submit for the audit/approval trail, then the corp card gets paid on the back end. No manual entry of expenses, physical signatures, physical checks, or !manual card payments. Coming from doing reports in excel, getting physical checks, and making payments myself on a company issued AMEX, I'll take Concur ANY day of the week.
I can see the added level of complexity of booking travel through Concur possibly adding frustration but I'm lucky enough to get to book my own travel myself without need for preauthorization.