The barghest has gone through several changes with the changing editions of D&D. I personally like the pack approach to hunting and growing better than the solitude. What I like most is making them the power behind the power controlling a large goblinoid tribe/war band. Sure, the goblinoid with shaman or druid, barbarian or fighter levels may be the "leader" of a tribe. But how did they get there, probably with the help of a barghest. How many savage species leaders have a pet wolf/dog/bear/boar that stays with them pretty much all the time?
Depending on which version of the barghest you are dealing with, will greatly strengthen or weaken them against the PCs. The version that gets sent "home" after being hit with magical fire is almost useless in 3rd or 4th edition due to the prevalence of groups with magical fire. However, in more old school games, magical fire was pretty rare and really powerful, especially in games where mages don't get to pick their spells. Also, their abilities change fairly significantly from version to version, I personally prefer the later versions with their blink, dimension door and misdirection abilities. I have been known to put one in charge of a pack of fiendish template blink dogs (FBD) that caused a party wipe due to the PCs trying to enforce their standard "fighters in front, ranged in back" battle tactic. Granted, they did kill the barghest, but several of the FBDs ripped the druid(not really a dedicated healer) apart in three rounds. Without heals, the barghest and FBDs just kept falling back after they would trip the melee combatants and do some damage to the casters/ranged slowly wearing them down, then cutting off their escape route. The barghest went down when the barbarian and ranger both got critical hits back-to-back (about 35 points of damage effectively instantly).
Anytime I have goblins (and most of the time any goblinoids) I have wolves mixed in to create a more realistic feel of the combat and to keep it more entertaining. Since barghests are almost indistinguishable from wolves/dogs, they make a great addition to a chaotic combat, despite their LE alignment. And they have a very respectable intelligence making them capable of using their "allies" to the advantage and knowing when to slip away if the fight is going against them. When you combine their intelligence with goblins natural capacity for making traps, the combo can truly be wonderful and I never feel like I'm cheating the players by making goblins overly intelligent or capable.
Barghests lose a lot of their effectiveness with the inclusion of a paladin in the party, which is more common in newer editions due to paladin being a class available to every race. But if you've got an old school group who like challenges and being surprised, a barghest is a great addition to your game.