Greg was offered the chance to be a field CSI and is supposed to still be in training for it. We see bits and pieces of him training for it now and then.
Remember he lost it when he was on scene in that ep about the bus crash - and he was sent "in the field" by Grissom and Nick to look for the silencer used in this season's 2 parter about that couple that had sex with other couples and killed them. He was griping because he thought he was getting real CSI action and instead he had to wander the streets looking in the trash.
I like that they're taking it slow with Greg's promotion and like that they're showing that maybe he's all gung ho for it but he really isn't cut out for the blood and gore, that he's better in the lab. I can't stand that other lab guy, he's so snarky and obnoxious. I wouldn't trust him to do my tests the right way.
I totally agree - no one needs to be promoted. In real life, I doubt CSI's get promotions every couple of years, so why rush it on the show? There's a nice hierarchy with Grissom in charge, then Catherine after him and then the three peons after her. Promoting one over the other two just seems like a silly way to manufacture tension.
Maybe I can hope (I know you're not with me, lol) that Griss will turn her down and Sara will get ticked and move away. He was great with the dominatrix and even better with the lady that does heads (I know, that sounds bad). I don't think his character would move on a relationship with a close colleague, no matter how much he liked her. It just seems...un-Grissom.