The blade of the Tomcat is now made with nicely finished VG10 steel, versus AUS-6 on the older versions.  Agressive thumb ridges on the spine of the blade allow for better grip and downward pressure.  The handle is still made from diamond point Kraton, and has a lined lanyard hole at the back.  The body has sculpted grooves over the thumstuds for easy opening.  
All Sog knives are guaranteed against defects in workmanship and materials for the life of the original purchaser, so again, keep your receipt if you buy one.  As with any Sog knife, you can get it engraved from the factory for $12.00... a nice touch.   MSRP on the Big Tomcat 3.0 is $200, we have seen them as low as $130 at some online retailers though.
If you dont want to sharpen your own knife, SOG will gladly do that for you for a mere $9.00 per knife...  which might be worth doing if you're not comfortable sharpening a knife that you just paid $200 bucks for.  That said, VG10 is not a terribly hard steel to sharpen, just make sure you practice on on your old timer first.  
If you are ever in need of a high quality folding survival knife, this would be an excellent choice... of course provided you use it and not mount it in a display case when you get it home.      
 

Close up of Arc-Lock on SOG's Tomcat 3.0