Jeroen's plugins are nice (even though the GUIs are tiny). I bought Izotone years ago and did use it a couple of times, but mixing on head phones never really worked well for me - even when I thought it did.
You always perceive sounds quite differently on head phones (with or without tools like Izotone), and there is also the psychological problem of knowing (and feeling) that there is something on your head which does not allow you to "believe" it's a real room you mix in.
In fact I've never heard a really good phones mix yet.
A big problem when mixing with head phones (especially without room simulators like Izotone) is that the ears get tired much sooner than with speakers. It only takes - at most - a couple of minutes, and you think everything you do sounds right, even though it actually sounds terrible.
Besides, you destroy your ears that way. But I think that's clear anyway.
Regards,
Steffen