Don't forget, new weapons aren't designed to be straight improvements. Yeah, when you see an ubersaw and a blutsauger, it's hard to really justify using the alternative, but they are still a trade-off of some kind for a bonus of another. The unlockables don't improve the class, they diversify it. So when contemplating new weapons, you should think of some bonus and some penalty the weapon would bring to the class.
For example, if you cover up a class's weak point (such as a spy's inability to shoot his disguise classes' weapons), you need to take away a bonus (such as a spy's ability to cloak, or only make them able to cloak for X seconds instead of Y, etc.). From there, it's up to the player to say "Hey this works better with how I play," or "No, this isn't worth what I have to give up for it."
Sadly, though this may have been Valve's intent, they did not implement it well in the medic patch. Two of the weapons (blutsauger, ubersaw) offer minimal trade-offs for substantial bonuses. The third, the Kritzkrieg, is so situational that it's hardly worth the trouble to equip the darned thing when you want it, provided you even know ahead of time when you will want it. Better off to just stay invulnerable with the regular Medigun.
Anyway, just my two cents, slightly off-topic though it may have been.
