My definition of a generalist unit is one that can do many things well. That is the main appeal to me of Draigowing. Generalists seems to be somewhat of a trademark for Space Marines in general (no pun intended). At the opposite end of the spectrum you've got eldar where most units are highly specialized. In between the two extremes it seems to me there resides most everything else. There are some armies that do mostly one thing well and if they do that very well then they can succeed - I'm thinking of Imperial Guard. While Grey Knights are a very good generalist army there are also the Space Wolves. While there are some things like JotWW I don't like I wish that every Space Marine codex was written to the same level of the pups minus JotWW. There is finally some balance now across the spectrum now with Necrons and suddenly Tyranids are competitive again.
To me the defining point of any army is their scoring units as these must win the games now that objectives are so prevalent. I have found that a five man Scout squad can win a game... It seems kind of crazy but then again to me it just makes good sense. In terms of scoring units I think that Tyranids are at the top with a plethora of devirsified troop choices - gants, genestealers and Warriors... They are really good at what they do plus gants can be buffed by some of the synaptic units such as the Tyrant and Tervigons. While I love Tyranids the most I know that there are others of the Hive mind that rival my thoughts and to them I can only say Exalt!
Here is my current pure Grey Knight army I'm playing:
3x psycannon & daemonhammer
Psilencer & daemonhammer
5x Strikes - psycannon
Landraider Crusader - psybolt ammo
Stormraven - twin linked multi-melta, twin linked assault cannon, hurricane bolter sponsons - psybolt ammo
Nemesis Dreadknight - personal teleporter, Gatling psilencer & heavy incinerator
The army is designed to throw down a lot of firepower to blaze infantry based armies, wreck transports and ground flying monstrous creatures. 40k6 is all about balance and while this list is very low on model count it can do just about everything and that's why I like it so much. In fact I'd go so far to say it is one of my favorite armies ever.