Gonna chime in along with everyone else here and, yep - tell ya the same thing. So far in the world of vaping there hasn't been an e-cig that meets BOTH of your criteria - all-day battery AND "looks like a cig".
With that said, I use a 510 and get about 3-4 hrs of battery use before I have to switch batteries. I use a PCC (which has it's own battery that lasts all day on a single charge) and it recharges my pv batteries in about an hour - so I'm never without a fully charged battery. The 510 is about the size of an analog cigarette. I bought my 510 starter kit for about $45. The PCC was extra.
I have never tried an eGo or Riva (Riva is the same thing as eGo, just rebranded), but from everything I've read and seen in reviews, it is a fantastic device for all-day vaping. It is slightly larger (fatter) than an analog, but that's the trade-off. Bigger battery = longer use. I'm not sure about the pricing on the eGo, but I do know you can get a Riva starter kit for around $30.
So there you have it. You'll just have to decide what is most important to you - something that looks like a cigarette that has "short" battery use, or something that is a little fatter that you don't have to worry about batteries all day.