My main, Blue Rush, is a kin/sonic.
What I can tell you from my experience with it is that:
1) It's great fun! Kinetics is a wonderful powerset capable of twisting around the outcome of a battle, speed up your team, make it more efficient, heal it proficently... All in all it kicks [censored]. Just be prepared to meet people that have two opposite reactions to SPEED BOOST (one of your most importante buffs): A) Love it like their mother, and scream the very moment it wears off: "SB PLZ!!!", or B) Hate the +speed factor of it so much to decide to give up the HUGE boost in recovery, recharge for all powers and endurance that you can give them. Unwise, but I've found more than one player who asked me not to buff him...
Sonic attack does not have many "special" attacks apart from Siren's Song and Dreadful Wail, but it's a very powerful set because each attack debuffs the resistence of the enemy, these debuffs stack and therefore every blow is gonna do more damage than the previous one (to a certain extant, of course the debuffs are not lasting forever!); paired up with hasten and syphon speed it is a vey powerful weapon.
2) It's a set that really shines in a team. In solo playing, you're gonna have a tough time, especially in the very beginning. I must say that after level 30, single origin enhancements and after placing the right amount of slots on the powers I've found Rush much better in solo play, especially the sonic attacks seem to do very few damage at the lowest levels compared to other DEF secondaries but become a lot more powerful as you go up to higher levels. I think that at a higher level you get more advantage from Sonic's debuffing capabilities, so be patient if you think you're not doing enough damage at the first levels; this will change, in time.
3) Kin/Sonic, due to Transference, Syphon Speed and to the relatively low cost in End for the Sonic Powers, is one of the sets that can actually be good without Stamina. This leaves you some room for other powers of your choice, and it's a nice benefit I believe, not to be forced to take 3 powers just to have Stamina. Of course this needs to be properly planned and slotted to work, but it works.
That's it for now. For the build, I think I will post mine in a few days to get opinions from the fellow forumites since I want to plan the next levels (I'm currently 35) and I still have an unclaimed respec, so stay tuned 
im going to role a kin sonic as my main. anyone got tips , advice and a build for it ? thx