T&M, service work, bid can all work out well depending on your customer base..

We have large oil producers which we work 30+ wiremen/linemen 40+ hours/week.. on T&M (Well, the T part.. They have their own accounts for material.) But aside for charging out for personnel; trucks, FR, personal H2S monitors and cell phones for foreman and above are charged out as well.

Me, my truck, cell phone, monitor and FR costs our customer $685 for an 8 hour day. I take care of whatever their I&E department requests from motor changeouts to instrumentation troubleshooting to cogen maintenance. Our company has weathered California's ugly economy surprisingly well.. We also have a few guys as part of a call out service department that stay generally busy as well.

Some of you know I used to work for a flat rate service contractor that paid us commission on the jobs we "sold" and completed. (Electure knows ALL about it LOL) Large full page phone book advertizing was their lifeblood and they were constantly busy. I cleared $100K/year working for this company and their yearly profit was upwards of $20M/year.
Their demise came not from lack of work, but from greedy management that refused refunds when someone screwed up and from hiring people who could "sell the job" but didn't know the difference between an I-beam and Jim Beam. They had no business attempting electrical repairs.

Scott (Electure) and I both worked for a company that did predominantly bid jobs. They had good relationships with a handful of general contractors that kept us busy. It wasn't the best paying company, but their checks never bounced and I had a steady 40 hours a week.