PMs are pretty neat, yeah. They run off Paradox instead of mana, which is... hrm.
Base rundown of paradox: Casting spells
generates paradox. There's no (hard) limit to how much paradox you can have. However, the more paradox you have over certain thresholds, the more likely things will go tits up and you'll blow yourself to kingdom come, or achieve something functionally equivalent to that.
Moreover, most of your spells power (and occasionally other things, like duration, etc.) scale with paradox -- the higher your paradox, the more damage you do... and the more likely your spell's going to explode in
your face instead of the enemy's. Paradox magi (and their more physically inclined kin, the temporal wardens) are therefor all about risk management, right down to their primary resource. Do you keep paradox low to avoid potential mishaps or let it scale on up and blow everything away (including, occasionally, yourself) with paradox boosted doomspells? A happy medium, perhaps? It's up to you, and how lucky you're feeling that day

PM talents also get pretty interesting (they're in the
chronomancer metaclass for a reason

) but I'll leave details as to that for if Dr.F decides to run one.