The Siren was a great boat for me at one time.  My learning curve really shot up when I got in it.  It's so limited though.  I hate it on a wave and in a hole and forget about loops!  It's great for gettting vertical but it is so pointy it is difficult to maintain it there with any control; it just wants to slice out from under you.  I am on the never ending quest for the perfect playboat.  I don't want anything too aggressive because I am definately more into river running than playing and I want to be comfortable on big pushy water in it too.  I have a squashed Spin I bought from Kat Levitt, and I love it, but it does a number on my back (which has been injured in the past).  So... the search continues, and in the meantime, I just want to be able to be comfortable in that damn Siren :)  My biggest problem with the sled is that I have to pull it all the way forward and then when I push aggressively with my feet (like when I get vertical) it pushes out and I am loose in the boat!  So aggrivating.  Anyway... thanks for all your input.  Maybe I will give it another shot soon.  
Laura