The Sherlock has a tiny sidecut radius so it rides shorter than it is on hardpack, so you can really get either your regular size or size up. I normally ride 162-64 boards but went with the 160 last year. I had no problems with float and it was great for resort too. That size would be my do-it-all size. However, at the end of the season I pushed out my stance, but still wanted the same size nose, so I got the 163. I only got to ride it once but it was stiffer and felt amazing. Really looking forward to this season.
The difference between the '12 and '13 is the addition of squeezebox tech. I don't know if it's better or not, but I think that squeezebox is here to stay so whatever. I found the '12 to be awesome. If $300 is a great deal for you then grab it (if new). Or wait til you get to Japan. In Japan, the sherlock isn't popular at all (I think just a lack of marketing or sales knowledge out there) so there's lots from last year still around. Banking on finding your size though, is a gamble.
I wouldn't put the k2 happy hour in the same category as the sherlock. The Happy Hour's tips are just for show and do nothing for pow. In the same category as the sherlock, I'd put the gnu dirty pillow and I guess the powder snake