I'm going to use Rodrigo's template here as it's well put together and should make comparing this all easier.  That's the hope at any rate. 
Character 
I was playing Artorius, a Strong 1/Charismatic 5/Fast 1, character.  I like this system better than standard d20 because it is more flexibility.  That said, I prefer even more flexibility, such as that found in classless systems.  This is a preference and not really a criticism as such.  I like talents.  I wish Artorius could have been a somewhat more accomplished fighter (beyond my abysmal rolling, I mean! 

).  The charisma feats (frightful presence) were cool as well as the talents coordinate and inspire.  Very cool option, that.  
Combat 
I liked the combat system, including Fewer Dead Heroes.  I'm usually not a huge fan of the defensive bonus thing, but I think it's necessary in a low magic game for survivability reasons.  It certainly made our characters more survivable, along with FDH, which I also like.
Action Points
I'm going to disagree with RB and say that I loved the way action points worked.  In my current D&D game we've been using a version that isn't quite as flexible.  I guess it reminded me of the various pools from my favorite system (Shadowrun) and I enjoyed having that sort of ability to influence what happened...except when I was rolling 1 after 1 after 1. 
Horror Check 
Oops!  See below.
Spellcasting
Can't talk too much about this, as I was not a spellcaster, but I generally agree with RB on the flexibility issue.  I think spellburn is a little harsher than I would prefer it, but were I to run GT, I'd probably house rule it a bit.
To conclude, I really enjoyed this encounter with Grim Tales.  While some of it is certainly attributable to the pleasure of the company, I do think it showed me how good D&D fantasy can be, something I have often found myself questioning over the last six months or so.  
I had intended to cease my purchases of d20 material in favor of other games, but I believe the next time I have cash to burn, I will seriously consider purchasing Grim Tales.
Anyway, hope some of that makes sense and is useful.  I'm certainly willing to entertain further, more specific questions.  I've had a long day, so I may have not been as eloquent as I might have liked. 
