I'm a freelance dev and I agree with Jonathan Stark that hourly billing incentivizes freelancers to inflate estimates and incentivizes clients to commoditize your work and to let scope creep.
Ever since I read his stuff, I've been doing value-pricing, i.e. "here's what we both agree will solve your problem, and here's 3 price options, depending on my level of involvement".
Then if I can get it done in an hour or in a year, either way I get paid the same and the client gets what they paid for.
Realistic time estimates, though, are a separate matter.
http://hourlybillingisnuts.com
Ever since I read his stuff, I've been doing value-pricing, i.e. "here's what we both agree will solve your problem, and here's 3 price options, depending on my level of involvement".
Then if I can get it done in an hour or in a year, either way I get paid the same and the client gets what they paid for.
Realistic time estimates, though, are a separate matter.