Which ORM use alongside codeigniter

[eluser]Patroklo[/eluser]
I'm thinking of go full ORM into my new codeigniter developments. But I have a lot of doubts, that I think everybody would have in my situation in the moment of choosing a good ORM engine.

I know that adding an orm layer always it's a minus at performance in every language, and also that it will consume more memory than "normal" querys, but I think that if the slowness it's not very high, it would be a great help developing in codeigniter.

I have been playing a little with Doctrine, that seems to be the most famous on PHP right now, and also I have used it in some benchmarking in my own computer and another server, but I have discovered that it's very slow(like 5-10 times slower than normal php or even codeigniter active record using the same object hydrating in the $query->result() function) and also uses a incredibly lot of memory in big querys(in a 8,000 row fetch I got a humoungous 20mb of memory consumption versus the active record object hydrating, in the two querys I finally had the same array of objects, I think that's just ridicolous).

So I'm just wondering which experiences do you have with Doctrine and if you could recommend me another ORM engines, and if, seeing this performances, even makes sense to use them.