No, it's not. There still exist a good number of mp3 decoders that can choke on id3v1 tags, whereas id3v2 tags are explicitly engineered to be transparent to any mp3 decoder. Add to that the fact that it's easy for them to be unsynchronized (due to fixed-length buffers in id3v1) and it should be easy to see that you should never have id3v1 tags.

Continuing to support id3v1 only supports lousy software engineering.