Yeah, I have Number 3 too and I'm still really enjoying this series.
Now a quibble. I know in the original books the turtles all wore red for their bandannas and the different colors were more of a product of the cartoon and Archie comics line but when you've got four main characters that look virtually the same those different colored bandannas can go a long
way towards making the characters look different and identifiable. Right now the only real way you can tell the difference in the turtles is their skin is colored slightly differently and the belt/weapon they have on them, (though everyone wears a single waist belt except for Leo who has the straps to support the scabbards for his swords and they don't always have their weapons on them or readied in such a way to make them visible.) It seems as their different personalities that were a product of the cartoon (Michelangelo being a "party dude", Donatello being into machines/science, Leo the leader, Raph the loner) that they'd have kept the different colored bandannas.
They maybe didn't have to use the colors used in cartoons for the different turtles but some physical trait on them should be greatly different enough so that they don't look all alike, right now it's pretty much through their dialogue/personality which doesn't always come through in word/thought balloons.
After the backstory on how the turtles got made I sort of expected the cat-villain was the same cat who made off with Raph, seemed likely the cat was exposed to the mutagen as well in the process. But, yeah, it's been an enjoyable series and I like the treatment of the turtles, Splinter and Casey Jones. Be interesting to see how much more April will be used in future issues and, yes, when the Shredder is finally introduced.