Two Types of Jobs

There are basically two types of jobs available on oDesk: the fixed-price and the hourly. Let me try to differentiate the two:

Fixed-Price: This type of job does not require contractors to log on to the oDesk Team Room Application (but it is highly suggested). Though the deadline for the task is provided, the employer does not pay you for the number of hours you worked but rather on the quality and/or quantity of the product/end result. 

Bad Side: Since you are being paid based on the service you've provided, it is the prerogative of the employer whether to pay you or not. Thus, many contractors suffer from scam employers. I for one experienced the same thing. My contract said that I will be paid $50 for the 250 comments that I will make on the employer' website (though my proposal was $80, he started my contract at $50). After finishing the task, I was only paid 

8-freaking dollars ($8)!! And he wanted me to do other tasks to be able to get the remaining $42. Don't get me wrong here, I did a great job based on his response. I guess he was really taking advantage of his employees because my co-contractors experienced the same thing. So what did I do? Nothing. I just ended my contract (and unwillingly gave him a feedback) because if I report him, he might just give me a poor feedback which can be an eyesore on my Contractor's Profile (but it is up to you whether you want to report him or no). From then on, I concentrated on applying for hourly jobs.

Hourly Jobs: The best part of this type of task is that you are guaranteed to be paid by your employers. You see, according to one of my co-contractors, employers cannot hire contractors/applicants if they have not verified their payment methods (ex. verfied his visa card). This helps eliminate scam employers. 

Bad Side: Actually there are no negative point about it, for me. But if you are the type of  person who hates coming to work at 8:00 am and logging out at 5:00pm, then you would, somehow, hate this. Most of employers  will require contractors to be online at a given time (usually following their timezone) for a given number of hours per day (on jobs like virtual assistance, customer service, database administration, etc.). Every now and then you will be asked to generate a weekly or monthly report. It is like you have a 8-hour job, only that it is virtual.

If you ask me which I prefer, then I will say the hourly jobs. 'Bet it's what most contractors would say also. But if you are (as you say in your cover letter) a "risk-taker individual", then go and apply for the fixed price ones. Who knows, you might end up working for a high-paying employer.