I had a 6D5N trip to Ijen, Mt Bromo and Borobudur with a superb companion, Sofyan recently (Sep 2016). This was a very enjoyable trip because Sofyan is such a fun, caring and detailed guide. He can speak good English which is the most essential factor for many travellers. He was recommended by my friend who followed his trip before.
I would recommend people to visit Ijen even though it is not as famous as Mt Bromo. The experience to see the “blue fire” is a must try experience which i think you should have but you need to have a fit body as well. Mt Bromo of course is not to be missed too.
I would highly recommend you to hire Sofyan as your guide should you intended to visit Indonesia. His passion towards tourism is what lacking in many and we need encourage more peoples like him. He has more fun and unique places in Indonesia to recommend to you which still waiting for people to explore.