Negotiation authority usually comes after being a GS-13 for a year, though you have to pass the certification exam before you become a GS-13. This new standard ends up being far more difficult than the old standard and likely exists to keep examiners in the fold. As a former examiner, I wouldn't want to leave unless you need more action at work than reviewing patent applications. I left for an IP strategy job and hated making the decision.
If you wanted to work as hard as an agent while at the PTO, you could make much more than an agent. It's just that the overtime and bonuses aren't required. If you need the money, the work is there for you. If you don't, a flexible 40 hrs schedule with a good home life isn't too bad. So long as you stay on top of your production and quality, they'll give you almost all the freedom you want.
Flip side of course is that if either slips, all perks go away, and stay gone for months. No OT, probably no bonus', and definitely no flex time. It's a great place to work, but, despite public opinion, they don't put up with poor performance.
If you get an offer - take it, rent at the Meridian at Carlyle for a year, walk to work, get promoted at 6 months, save up for a condo, don't buy a car, join the PTOS, take the free shuttle to Old Town and the waterfront in the summers, get promoted 12 months after your 6 month promotion, buy the condo which will be built in 2008 by a metro stop but not on the green line, see if you can hit your 130% bonus, get it for the first time, dance, find a nice girl in Olson's bookstore on the waterfront, marry her, move into said condo, live happily ever after.
p@tent.guy