Jeanette,
Even forgeting the free pricetag IRIS ts an amazing piece of software and the interface has improved greatly since the earlier version. If you follow the tutorials you'll soon get the swing of things.
Nice features of IRIS include:
1. RAW file conversion of DSLR files is excellent.
2. Star field registration capabilities excellent (for example it can compensate for shifts, rotations and distortion between images).
3. Background gradient removal is one of the best I have seen.
Re the interface, some things seem a little unconventional. For example if you want to batch convert multiple raw files you click the 'Decode raw files' menu and a blank window appears. You then use windows explorer to drag and drop files onto that blank window then when you have finished click convert. Its actually efficient, but doesn't follow normal MS Windows conventions. After you come to terms with this you begin to realise what a fantastic bit of software it is - I swear by it
Terry