The Damage Conversion bit takes a bit to get used to.  I'd say about one session before it becomes unconcious.  It adds a little math, but the same little math as having some DR.  You end up with a double-column of HP, though.  The same rules have always been there (from D&D, anyway) but they don't come up as often until you go with Damage Conversion mechanic.  
It adds a cushion between unconciousness and death.  It also adds in some of that "we're the heroes" of VP/WP by adding in some "VP" that will return after a few hours from the NL damage.  The heroes can recover a bit of their HP from an hour or two of downtime, but they can't just return to full strength (as most armor isn't going to fully convert incoming damage to NL damage).
I don't adjust the MDT stuff on the fly (yet, hrm, might be a situation where it would work).  Usually I "set" them based on the parameters of the campaign I'd like to run.  More heroic, MDT=Con and DC=15.  Don't want good shots to become small threats?  MDT=Con, DC=10+(0.5*Damage).  
My gritty sci-fi western is MDT=10, DC=10+(0.5*Damage).  
You can choose to do Damage Conversion before or after checking for MDT, which changes things again.  I've only used Before, myself, but it would increase the MDTs to do it after, especially with the lower thresholds.  Before the threshold, effectively, includes the Armor.  So, say, if MDT=Con and armor gives conversion, a guy in +9 armor is going to take a BIG hit before he even has a chance of going down from the damage alone.
--fje