Ditched the laces on my work shoes, and went to the slip on style. I'll never go back to lace up shoes again unless I have to (sports stuff). They are just so comfortable, and convenient.
For my old work boots though I bought some laces from lee valley that varied the thickness along the length. They never came undone unless you wanted them too.
Edit: found them http://www.leevalley.com/en/garden/p...,73350&p=70253 They worked great and didn't break the bank.