SF/TWF/TWD... eh.
I'm not entirely convinced this is the best expendature for feats for an implement user. Sorcerers might want some spell fury in there.
I'm playing a staff wizard and was looking at those feats. I think Staff Fighting can be worth it, but TWF/TWD don't cut it for me. Assuming you take Dual Implement Spellcaster, and your off-hand implement has an enhancement 1 less than your main, Staff Fighting is effectively +1 AC and +1 damage, which is quite nice for a single feat. After that, TWF and TWD give you the same benefit (and +1 Reflex), but for two feats -- not nearly as good a deal.
They're still decent feats, but if you look at everything else you'd definitely want to take first...
- Staff Fighting (+1 AC and +1 damage)
- Dual Implement Spellcaster (better than TWF for damage)
- Weapon Focus (at least as good as TWF for damage)
- Leather Armor Proficiency (better than TWD for defense)
- Implement Expertise
For wizards, I'd also add Enlarge Spell and maybe Improved Initiative or Destructive Wizardry. With the PHB3, there's also Superior Implement Training.
So that more than fills out your heroic feats... then there are some great paragon feats, depending on your focus: Arcane Admixture + Resounding Thunder, Psychic Lock, Spell Focus, etc.
After all that, you're probably at least at mid-paragon before getting to TWF and TWD. They might be decent choices at that point, but +1 damage at mid-paragon isn't too exciting.