I've played both of these side by side (reshafted with the exaclty same shafts, grips, lenghts and swingweights):
PING I3 blade 7 Iron : lenght 36.75" loft 34.5Ā° lie 63Ā° (black dot) sw D1
PING I-blade 7 Iron : lenght 37" loft 34Ā° lie 62Ā° (+1Ā° blue dot) sw D2
Marketing said every new club was longer, straighter and more forgiving then the one from the previous year. With the I-blade the claim was only straighter and more forgiving but not longer since the set was made (on popular demand) with old school lofts. I did not find any difference in playing lenght, ball flight or dispertion with center and off-center hits. Only had a small preference in feel for the old I3's, so I sold the newer I-blades. Compairing clubheads with the same specs but 17 years of technology apart did not convince me of a lot of progress.