Sweet! I just got the plan switched over. I'm in Oakland, CA. I printed up the plan and went to the Broadway Sprint store. They said they couldn't start the plan there, but I could start an account with them and call CS. I also managed to get them to price match wireflyfriends.com's offer on the A900 and got it for 139.99. Total I paid out the door was 150 w/ tax.
After some struggles (stupid *2 line kept routing me to a message saying the office was closed) I was able to talk to someone from the business dept. The number you want to call is 1-877-812-1223. The CSR was very pleasant was definitely from the midwest I believe (had a southern twang to her voice). I did have to call 3 times to finally get a hold of her (I was dropped the first two times). She knew exactly what I was talking about and all I needed was an email of the employee who referred me.
From her explanation, the SERO 500 is just a discounted version of the fair & flexible plan because you still get charged $5 for every 50 minutes you go over. It also has several free promotions lopped into it, so when you check it online, it will say Fair & Flexible.
I am loving the A900, but I have to agree with NYCFella in that it does not have a very long battery life when you're streaming live content, but the EVDO is freakin awesome. It totally blows away my girlfriend's Verizon Treo on web speed.