We started Ptolus in Rolemaster and I must say it is a blast!! I didn't GM this as my nephew wanted to run it. After the first session, we are in for it that is for sure. The city is so complete and we started in the slum section (and are still there), really a lot of fun. Especially since Rolemaster is so detailed with Cultures and Regions(we have wards of the citiy as our regions) the game is a blast.
Initial party is a Magent (me), Dabbler, Rogue and Fighter. We are trying to find our way but started out as indentured servants with nothing but a pot to tick in. Real good concept and are slowly learning about all that is Ptolus. It is real easy to convert and move over as Monte Cook did a superb job in the details. It is High Fantasy so I would recommend the PDF download ($60) for anyone who wants an awesome world to play Rolemaster in.