(I'm torn where to post this, my personal review of the Rally kite, but since I don't pay full retail for my Slingshot gear, I'll post it here in "Industry Soapbox". That said, this is MY opinion and I'm not paid by Slingshot or anyone else to pimp their gear).
I've flown the Rally kites since they were introduced in 2011. Being that I kite in waves around 85% of my sessions, the Rally has been a good match for me.
Like other brands, Slingshot has made changes to their kites from year to year - the Rally is no exception. Primarily, they've played around with the shape of the wingtip and rear attachment points. They were quick to redesign things when an issue was discovered with wingtip wear on the original 2011 kite - users found a place where the steering lines were rubbing the wingtip in a bad way. If you're looking at used 2011 Rallys, see this thread: http://www.bayareakiteboarding.com/forum/viewtopic.php?f=1&t=10202&p=69088&hilit=rally+wingtip#p69088
The 2011 and 2012 Rallys flew very similarly. These kites were fast and felt very 'light' in the air. While they turned fast and drifted down the line superbly, they weren't as stable as Slingshot wanted and could be seen visibly racing forward in the window in gusts. They all flew fine, but in classic kite manufacturer form, they seemed to need to change things from year to year.
In 2013, Slingshot made the Rally more grunty, but these models sacrificed turning speed, particularly in the 10m size. I rode my 2013 10m rally at places where other people were on 12's (other brands) and I was happy with the low-end of the 10. But in comparison to the Rallys of earlier years, the 2013 in larger sizes felt slow in turning. The 2013 6m and 8m Rallys remain in my quiver and I'm totally happy with those sizes.
(there isn't anything wrong with the 2013 10m. In fact, it flies great and has lots of pull. I only mention this if you're used to the turning speed of the 2011/2012 Rally, the 2013 will feel different compared to the older kites. In fact, I'd recommend the 2013 10m Rally for beginners and intermediates who are looking for a predictable and stable kite with great relaunch.)
I recently flew the 2014 10m Rally in the waves and I'm happy to report that it's back to it's fast turning roots. From the moment I launched the kite, I could feel the difference in turning. Simple wrist movements with the bar in one hand made the kite zip back and forth across the window - similar to the turning speed of the 2011 and 2012 Rally.
If you kite in the surf and/or want a kite that is well behaved in situations where you have little line tension (i.e. riding at the kite), I recommend trying the Rally. Relaunch is easy and the construction has (knock wood) been surf-tough. These kites self-launch and self-land well without jumping around or getting squirrelly.
Slingshot has also made some really nice design changes to their bar for 2014. For those of you who hate below the bar depower, you'll still be unhappy with the Slingy bar. I'd still like to see them soften the grip material a bit, but the new donkey is stiffer and less likely to come unhooked in critical situations. The release system still works the same, but the mechanism has been redesigned with a new metal casting which is simpler and cleaner. All parts are easy to get to and can be replaced if necessary. The little bungee which keeps the release handle down is now housed internally which should keep it out of the UV and presumably last longer.
I can't speak for the other sizes (yet), but the 2014 10m Rally is going to be a killer surf kite for my quiver.