If you have some knowledge in ruby it is not very difficult to start using rhodes, but it will always depend on your requirements and on how much time you want to invest to develop apps for different OS.
I have found Rhomobile very easy to follow. Of course it is limited as it is a relatively new framework, but you can get very good help on their Google Group.
I have developed on iOS and Android, and I must say I hated Objective C. Android with Java was more familiar and easier for me, but still, it is not compared to doing one app that works for all (even though you have to make dome minor tweaks for each OS).
One thing I did have problems developing in Rhomobile was working with maps. Rhomobile's Maps have different limitations depending on the OS of deployment.
Anyways, specially if you are working by yourself, I would recommend experimenting with Rhomobile. I believe you will get your job done faster that developing for each one (Objective C is a nightmare!)