That's partially because the concept of "weapliments" wasn't completely ironed out when the PH first came out, but was shortly after refined and clarified. I'll try to explain.
"Weapliment" is the unofficial term for items that function as both a weapon and an implement. Several classes, such as the wizard, sorcerer, and swordmage, get the ability to use certain weapons as implements. Additionally, certain magic items, such as pact blades, holy avengers, songbows, can be used as weapliments by specific classes.
The main thing to keep in mind when you use a weapon as an implement is that none of the weapon's mundane properties apply to your attack. This includes not only the weapon's proficiency bonus, as already noted in this thread, but also anything listed under "properties" on the weapon table entry (PH; pg 218-219), such as versatile and high-crit.
Note that I bolded mundane. The properties of magical items still apply to your implement attacks. For example, a wizard using a quaterstaff with the Subtle Weapon enchantment (Adventurer's Vault) could gain the item bonus to damage with both her weapon and implement attacks.
And finally, one more important note. Weapliments are still considered a weapon of their group when used as an implement. This means that powers, feats, and abilities that trigger off of using a specific group of weapon function when using said weapons as implements. For example, when a swordmage uses a rapier as an implement, it is still considered a light blade. Likewise, a swordmage could apply the Light Blade Precision feat to implement attack made with a rapier.
Correct. Your standard, mundane implement does not provide any enhancement bonuses to attack or damage rolls. Just like how a mundane dagger or longsword does not provide any enhancement bonuses.
However, as you probably know by now, you still want to have a mundane implement if you have any abilities or feats that require an implement. Your wizard's Staff of Defense feature requires an staff, whether or not it's magical. Likewise, if you had the Staff Expertise feat, you would have to use a staff to gain the bonus to attack and damage
in response to a question on noob calculating attack bonus
Heavy Blade Expertise
Benefit: You gain a +1 feat bonus to weapon attack rolls that you make with a heavy blade. This bonus increases to +2 at 11th level and +3 at 21st level. In addition, while wielding a heavy blade, you gain a +2 bonus to all defenses against opportunity attacks.
Benefit: Choose a weapon group, such as spear or heavy blade. You gain a +1 feat bonus to the damage rolls of weapon attacks that you make with a weapon from that group. This bonus increases to +2 at 11th level and +3 at 21st level. Special: You can take this feat more than once. Each time you select this feat, choose another weapon group.
So I am a swordmage (or paladin with holy avenger or sorcerer with dagger etc) with heavy weapon expertise and heavy weapon focus - - do those bonus add (+1/+2/+3 etc) when using a power with the implement keyword (provided of course that i can use the said weapliment as an implement)?
And the collorary - - I am using a weapliment - - - lets say swordmage using any one handed blade - who has taken implement expertise
Heroic Tier Benefit: Choose a type of implement. You gain a +1 feat bonus to attack rolls with any implement power you use through that type of implement. The bonus increases to +2 at 11th level and +3 at 21st level. Special: You can take this feat more than once. Each time you take this feat, choose a different type of implement.
can the sword mage use the +1/+2/+3 when using the weapliment to attack using a power with the weapon keyword?