Before I take Bound weapons as a serious choice of weaponry, I have but one question.

When do they become worse than what I can make? Or do they?

I have some knowledge of bound weapons and what they're like. According to the UESP, with the Mystic Binding perk, the Bound Battleaxe (my choice) has a base damage of 22. That's about the same as an unsmithed Elven Battleaxe or Warhammer.

The character I plan to use them on is currently at 30 Smithing with a Dwarven Greatsword smithed to Superior. IIRC, it does little less than 40 damage at 50-something Two-Handed. Would a Bound Battleaxe be better or should I save a couple of perks and just keeping using what I can find/make and improve?

I believe Bound weapons are Daedric weapons so they have the basic daedric weapon damage and there is a perk that increases damage of bound weapons. I believe only Daedric (either normal or enchanted) or enchanted Ebony conventional weapons would probably be just as good if not better

I use bound weapons when I roll my arcane blademan character. Bound weapons dmg increases as you put skill points/perks in the relevant weapons skill tress (1H or 2H). They are extremely OP at the lower levels. If you pursue smithing, once you get daedric (and assuming you have all the weapons perks in the skill tree), you can smith a more powerful weapon. However, I have found that with just the mystic binding perk is perfectly fine for me. It really depends on how you wnt to play. If you want to make a wepon that one shots everything, then bound weapons are not for you.

EDIT: bound weapons are weightless, so you can power attack more often with them.

damage formula
http://www.uesp.net/wiki/Skyrim:Weapons

Dwarven Greatsword = 19 base dmg
Superior smithing = +3(base) dmg
= 22

Both have the same dmg, and speed (0,7) but bound weapons are weightless (they should use less stamina for power attacks)

Edit conclusion
- A Dwarven Greatsword with the 2nd lowest smithing is on par with a bound weapon + perk
- Bound weapons can not hold enchants
- use a "real weapon"

So I'll think I'll try them out. I don't plan on getting Daedric smithing for a while, seeing as how I'm only level 12.

Another reason why I'll like them is because I use power attacks a lot, mainly to stagger mages. So the weightlessness will come in handy.