Originally posted by aurele i have to say : i've used 2 different 55/1.2 (Porst 55/1.2 - Revuenon 55/1.2) and they had nothing exceptional.
To me, the Da*55/1.4 is far better, and has probably a T-stop as good as those f1.2 lenses.
There are a few forum discussions on 55mm f1.2 lenses that are probably worth searching through - If I remember correctly the Ricoh is not a clone of the Porst or Revuenon, but may have been manufactured by Cosina or possibly Tomioka (depends on what you read). The Rikenon is generally quite highly regarded, and as I said earlier is in the same league as the Pentax 50/1.2's.
This guy has an interesting little read on the Rikenon:
Rikenon 55mm f/1.2 review | jonasrask|photography
The Pentax DA*55/1.4 is from a different world - the digital age, with improved coatings, a smaller aperture, computer designed, etc, so is highly likely to be a "better" lens - but sometimes it is the character of the older lenses that shines through (and sometimes not). My DA*55 is certainly one of the finest lenses I've used, but I'll still keep a 1.2 in the arsenal a little while longer