Not getting merged mined coins on p2pool
I also do merged mining with p2pool. Keep in mind that you are essentially solo mining for namecoin and iXcoin--when another member of p2pool (not you) finds a winning share that exceeds the target difficulty for bitcoin it isn't usable by you as a winning share for the other coins. So you can't leverage the efforts of the rest of the pool to help you find the other coins.

However if you (or other clients connected to your p2pool node) generate a winning share then you will see the altcoin blocks get generated. Given that you are solo mining for those coins it can take quite awhile before you get a share with high enough difficulty. But I assure you that it works.