Back in December, I put together a script for converting RightFields data to CustomFields. This was mostly for me, but I had a few people request this sort of thing, and I had grown tired of doing it by hand, since I'm inherently lazy. There were two problems with this script. The first was that it didn't do data stored in custom SQL datasources. Unfortunately it was just too hard to figure out. That's not to say that I couldn't make it work, but I wasn't able to do it in an automated fashion.
The second problem was that it left out a few people who had some data that they might want: Namely those with data stored in file fields (usually a file name, such as that you might use for an image). These fields can be somewhat complex, but if it's just a name, then it's not typically a problem in converting the data. So it may be okay to convert it. Still, you should probably be aware that a one-to-one conversion of this sort does have some potential pitfalls. The most common was that CustomFields doesn't have an upload option, but you also can't do things like extra file path information. So if you decide you want to convert the filename, you should be aware of these potential downfalls. It's better than nothing, however.