Previously, I'd stayed away from it. The payee-run version of it is something to stay the hell away from. I'm not giving a utility company my checking account number so they can debit what they like out of my account, when they want. If they fuck up, it's my headache, even if they do cover, or my bank forgives, any overdraw/overlimit fees. It's impossible to withhold payment of a contested portion of a bill that way. The utilities are also not allowed to auto-charge my credit cards. I let Speakeasy do that for my DSL line, but only because they have the (deserved) reputation of Having Their Shit Together, and unlike most utilities, they answer the phone quickly to solve problems.
The bank-end of it used to be costly and cumbersome. BofA has stopped charging to use their service, which is why I was willing to look into it. There is no way I will pay somebody extra in order to save them the cost of processing my paper checks. Now it's free, and it's a smart system that strives to do things electronically. All my utilities are paid electronically. My condo association will get a paper check this month. Friends tell me that once the bank has the relevant data from that transaction, they will switch that to electronic payment too.
What pushed me to do it is simply the headache of writing a bunch of checks every month. It's something that gets left until there's a stack of bills to be paid, and I'm forced to spend a half-hour writing so that I'm not late on a payment. Ugh. The interface is nice... BofA's web site presents me with a table of listed payees, each with a form field for amount and payment date. I fill in all the numbers for bills I want to pay, and click one "go" button, and it all goes. This is really cool... I hate having to repeat the procedure over and over for each transaction. It's one of the things that galls me about the sports scheduling services and sites I use (eteamz.com and LeagueSite/phpWebSite.) I don't like spending forever waiting for pages to load and submit, when I know it can be done once.
It may be a long while before I need to order checks again. Paying bills is all I ever use them for anymore. Outside of that, I maybe write half a dozen checks a year.