Same characters, different specs?

After doing a lot of reading here on the forum I took the leap. Now I have my 5 accounts, the EVGA GeForce GTX 560 2GB heavily recommended in a hardware thread, and dealt with customer service locking my accounts when they thought someone had hacked my account and started spamming out invites. (I invited 4 new accounts so I could get the 300% exp bonus.) Oh, and ISBoxer.

Now I have three groups to play around with.
1 Pally + 4 Shaman
5 Hunters (1 for each alliance race that has hunters)
3 Mage

I started with a 3 mage group to test things and decided to give each mage a different specialty. It made sense at the time. One with frost to slow the advancing mob with the other two have improved damage to take them down. Logically it might also help with mobs that have resistance to a line. After playing a while I am afraid that anything gained may be lost with variances in timing. Especially with the arcane line.

Now for the question. As a general rule should all characters have the same spec? Is it dependent on class? For classes like Shaman and Druid is it better to level up with one spec and then branch out at a higher level?

I like to keep them all the same while leveling, then once max level I worry about a final spec for everyone.

If they are all different specs, it feels like I have to re-setup half my spell bar every time one of them learns a new spell. If they are all the same it feels like more questing and less setup.

Going into MoP I think you'll want to run the characters as whatever spec you want them in finally, even while leveling, due to the way quest rewards are being handled now.

For example, my first team will likely be 5 x paladin but while leveling I'll be going with 1 prot, 1 holy and 3 ret just so when I hand in quests they get the spec appropriate gear. If I ran all 5 as ret then they'd only have the choice of ret rewards and if I decided to go level up in dungeons for a while I'd have to go and buy holy and prot gear for the tank and healer.

I had no issues leveling my teams with different specs. Out in the world, things die so fast and leveling is so fast that it doesn't really matter what your setup is. Most of the time I don't even bother with upgrading spells or macros for 10-20 levels at a time.

Like Knytestorme says, there's going to be spec-specific rewards coming with the MoP changes so it's probably going to be a better idea to just level as the spec you want so you're getting upgrades that you'll use. On the other hand, you could always level all the same until you get to 80 or so and then choose a final spec so you're high level quest rewards are useful. It depends on how you want to level. IMO -

As Fast As Possible - spec them all the same and don't worry about it until you're nearing the end of leveling.
Slow enough to hit dungeons on the way - choose your preferred spec early so you get the best gear you can on the way.