The answer for me is definitely 'Yes!'.
For the most part, I am a solo player.
I quickly get myself to the max level and then I go run the rest of the quests for fun.
I am not part of a large guild since I don't have a lot of evening time that I can always have available for raiding on a schedule.
Unfortunately, without a guild, it was very difficult to put together a pickup group (PUG) for an instance.
Let me explain the feature a bit more and then come back to why this is the best new feature.
Prior to the 3.
3 patch, putting together a PUG was accomplished by standing around in one of the major cities (usually Dalaran these days) and calling out in the trade channel for what you wanted to run.
Looking For Group (LFG) or Looking For Members (LFM - you had a partial group and wanted more members) were the keywords that you used or watched to let others know what you were trying to accomplish.
This mechanism still works in WOW, but there is a MUCH better way to do it now.
Blizzard introduced a new feature in the 3.
3 patch called the Dungeon Finder.
You can launch this feature by clicking the little 'rotating eye' icon that is next to 'Game Menu' icon.
The window that opens gives you some choices:

• which dungeons you are willing to attempt
• what role you are willing to take in the 5 man group.
  The 3 possible roles are tank, healer, and DPS (damage per second).
  Obviously, not all roles are available to every class.
  

Also, the window shows a reward that you will get for participating in the PUG - this is in addition to the normal rewards that you will get from the instance itself.
Blizzard wants to encourage you to use the Dungeon Finder tool and this is one of the incentives they are providing.
There are two other great benefits of the tool:

• The group is assembled from all the realms in your battlegroup.
  This means that there is a much bigger pool of potential players signed up and the wait to get into an instance is therefore much shorter.
  
• When the group has been picked, each player gets a notification.
  When all of the players have indicated that they are ready, the characters are teleported to just inside the instance.
  Whenever a player leaves the party (eg when the final boss is killed and loot distributed), the player is returned to their previous location.
  

This means that I can enter the queue for an instance and go run dailies, or fish, or anything else while I am waiting.
We are no longer trapped in the cities watching the spew to get an instance run together.
The only limit I have found is that you can't indicate that you are ready to enter an instance while you are in combat.
So, you need to finish your fight and then indicate that you are ready.
I have also been in groups that fall apart inside the instance.
In the old days, this usually aborted the entire run and wasted everybody's time.
With the Dungeon Finder, the party leader just queues the group for an instance and the DF finds a replacement character for the party.
In my experience so far, the wait times in the queues have been less than 15 minutes.
Since travel time is removed, this makes it possible to run several instances in a single evening of play.
Prior to the 3.
3 patch, I had not been inside any instance in Northrend (Wrath of the Lich King).
Now, within 2 weeks of the patch release, with only a couple of hours every couple of days, I have been through almost all of the 5 man instances in heroic mode.
This feature has opened up to me a part of the game in which I was previously unable to take part.