It is a light armored fighter without feats but with a few tricks. That said, you can cheese up a bit to compensate.
The DMG II has the Sudden Stunning weapon enhancement for 2000 gp - the stunning effect has x/day and save DC based on your chr mod, and the latter is also affected by your level (!).
The PHB II has a great alternate ability - the "dark companion" instead of a familiar. This one has no save, so you do things in the following order: Move Cat, Curse, then whack with your Sudden Stunning Greatsword.
You do have social skills so you can be the "Face" of the party, at least.
Avoid "Save or Else" spells. Most foes you fight will make their saves because you get your spells so late. The counter-argument is that you can use your Hex to lower their saves and balance things out. Don't listen to this counter-argument. Your Hex will work a lot better against the dude that your Wizard, Sorceror, Cleric, Druid or Psion buddy is about to use their own "Save or Else" spells/powers vs., and their save DCs won't be crap.
Beg your DM to be able to use the Hexblade feats from Dragon #339, or even the Reserve Feats from Complete Mage, in place of your Hexblade Bonus feats.
Since you are in Light Armor anyhow, you could go for those feats that only work in Light Armor/Light Encumbrance, but that is making a virtue of necessity.
Other than that, roleplaying wise it lets you be a bastard. I am playing a CN Hexblade that actually made and broke a deal with a demon before the demon could break the deal with him.
So I would say Hexblades can be fun, but don't expect to be the power house. It makes an interesting 5th or 6th character since debuffing the enemy is helpful to your buddies in a way similar to, yet distinct from (and stacking with), buffing your friends (the bard's job).