What have been your experiences with Monster PCs in your games? I am mainly talking about DnD 3.X and Pathfinder here, but anyone who has played or GMed a Monster PC under other systems is welcome to share their experience.
My friends and I have made frequent use of monsters as PCs, mostly templates but standard monsters as well. In the 3.X rules, we used the ECL rules although we often dropped them down a step because they seemed over called (that is, we would often use an ECL 2 if the MM said ECL 3 for example).
Overall, it seemed to work fairly well as long as everyone was within 2-4 ECLs of each other, depending on the overall level of the campaign. We typically did this in campaigns starting at level 6 or higher so that the class level for folks with ECL was still 4 or more. It seems the lower the character level, the more awkward ECL is so starting higher level worked better.
In general, while the PCs with an ECL were more colorful, they were rarely the same power as a character with ECL 0 (i.e., the normal races) but we liked the color of it.
Our character selection method allowed the players to choose their characters from a slate of figures, each figure having its own ECL and some other bonuses.
One of the most elaborate setups we did had 36 figures each with their own cards and ECLs ranging from 1 to 6. I put the cards together but I didn't paint the figures
Our group painter did those (you can see figures for our new campaign at
Affliction: The Draft Figures not as fancy as the cards below though and no ECLs since we are going with 4E races.)
You can find 2 pdfs of the cards at
Affliction: Ophir Draft for our take on how to include quite a range of creatures. Rule set was 3.0 IIRC.