I have had a few Slabbed coins in the past, I' am sort of old time when it comes to these. I feel that the "Good" points of haveing a coin graded is when you have a rare type of (Die Variant), or a 1922 p lincoln, 55 double die ect...or to authenticate a type coin. I do believe this will add some value premium to the coin rather than being in raw state.
On the other hand I have experienced Dealers who will push this as explained when they sell you these coins, but when you go to sell the same "Slabbed" variant coins, they wont give you the premium of being slabbed! they will just gray sheet you regardless (Wholesale), but will most absolutely charge you for the same coin slabbed when it's back for sale in their shop!.
So....The other helpfull advice for slabed coins is that it does take alot of the gradeing questions away from the dealers who otherwise would really "DOWN GRADE" your other wise "RAW" coins!.Yes, very few graded coins I will disagree with the grade, but all in all the coin has been checked-out by the pro's, so when I do sell my "Slabbed" graded variant coins to a dealer in the future, you bet if he wants it, he will pay me for it!!!!!!!Thats why dealers love it when you bring "RAW" coins in for sale, and hate it when you bring in "Slabbed" coins, because they know their chance for "DOWN GRADE" has been taken away but will still try and give you a wholesale "RAW" coin price.
I love Raw coins and will still keep them that way, only exception is the rarer types mentioned. Happy collecting!!

The way I see it.

Some Pros...
Authentication
A certain level of protection in price when buying and selling expensive coins
Good protection from the environment

Cons...
Not enough consistancy in grading which leads to
The Crack Out Game which leads to
Too much focus on grading and pricing and not enough on history and learning about the coin itself which leads to
Generally higher prices when buying
A false sense of security that the services don't make mistakes and are more consistant than they are
Ugly and bulky storage method

I could probably think of more but that is what comes immediately to mind. I am not anti-slab or pro-slab. I see them as a tool that can be used or misused like most other tools.

My opinion only. Your mileage may vary. Please don't sue me.

Let's see, this question definately has been raised several times on different boards and my opinions differs every time I see various comments. But here are some of my firm opinions.

Reasons to detest slabs:
1) Slabs remove the beauty of edging technology and to me, slabbing just means we are just basing on two 2D images, not on one 1 3D object.
2) Slabbing do cost a fair bit especially if you live overseas, everything adds up to some horror sum.
3) Slabbing appearently has raised the value of numismatics generally especially when it comes to 1 grade difference. And with this, we get all odd companies. My main concern is when China gets into such counterfeiting, and this will cause a total headache.
4) For awfully small coins, having too many slabs could be a pain. Imagine that you had 100 dimes slabbed. Unless they are of high prenium, wouldn't they be better off in raws?

On the other hand, the postive sides I believe are:

1) Top rated TPGs would usually identify various variants and one wouldn't need to worry much. Definately recommanded if you have some "rarer" coins to be slabbed for.
2) Selling is indeed a lot easier as most grades are not disputable and actually useful when you have an awful photograph technique and want to sell across eBay.
3) Storage wise, slabs are most probably the best since the coins are laid in plastic coffins and encapuslated in vaccum conditions if I am not mistaken.
4) Security wise, unless one is to crack the slabs open, coins are easily identifiable and reportable.

That's all that I could think of right now.

Another good reason to Slab a rarer type coin is upon your death, heaven forbid, your next of kin will get a fair assesment of you collection rather than being in raw state. Most kin will just want to sell and wont know anything about the coins or very little... Slabbing the "BETTER" coins, I would rest peacefully in my grave, (A little better!).

I have no problem buying slabbed coins, especially for my type set. When it comes to stuff like Trade dollars that are easy counterfeited, paying the extra few bucks to make sure it is real is worth it. Having die varities slabbed is a good idea as well.

Only thing I don't like is trying to image slabbed coins and the extra cash for the "common" coins.

You've got it covered