it seems my first post got voted out, so let me repeat the important information
keep in mind these are simply my observations since there is no info posted on the summoned creature Timbermaw Ancestor

-It seems to have ~500 hp
-It is level 60, but isn't very tough even versus lower level melee
-It seems to heal you ONLY if you drop below 50% HP, and this also seems to be subjective to if it's attacking something or not. You can exert some control over this by ensuring that all targets around you are CCd when you want it to heal you. As a rogue I blind, then gouge and start a bandaid while he casts a heal.
-I've seen it's heals range from 200-900 however I wasn't paying attention to mortal strike or critical heals.
-It spams a lightning bolt that is ~2 second cast time for 250 damage.
-It will not attack anything unless something attacks you while it's summoned, however it will heal if there are no enemies around and you are under ~50%
-It is obtainable for a level 49 (my 49 rogue has it, and i don't use it that often.)

This is a fun trinket, but if your going to use it in outlands, expect the bear to get one-shotted by aoes or adds. This bear doesn't have much life, like 300.
I liked to summon this guy in emercancys such as when your surrounded and need some heals or some quick damage on a foe.

It should also be worth mentioning this item is on the same cooldown timer as the summonable skeletons, Balnov Servants, Etc. Don't expect to pop this and be able to pop another summon trinket, as cool as it might be to summon a tiny army

The bears AI is very bad.
It will only heal you if your < 50% life and it will only wraith an enemy if you we're fighting it when you summoned him. If you have an additional target in a fight, the bear will not wraith him. So you must summon this guy during a fight and not before or you wasted the extremely bad cooldown timer of 10 minutes.

They should really make the cooldown 2 minutes or whatever for the absolute trouble you go through to get this guy.

Not worth it after TBC, only if they decide to buff this trinket, or you'd like the notoriety of having a summonable ursa to show your friends (like me.) This could also be an item you'd like to set a goal upon if you like trying to get extremely hard-to-find items or you like to challenge yourself.

When you finish the quest for this item your name will be shouted and talked about by NPCs in orgrimmar, which is kinda fun if alot of other people are playing, it is really nice to hear, "goob job", from other players after finishing the long rep grind. It also feels cool it be one of the few players carrying around such a rare item and you didn't get it 'easily' from some raid or some easier quest.

Don't expect other people in your PUGs to recognize this item and the trouble it takes to get it unless you mention it or they have one themselves, they will just think it's an ordinary epic trinket.

This isn't a good pvp item in my opinion because it takes too long for the ursa to heal or damage your opponents (for very little), and the other player can just one-shot it, easily.

It doesn't seem likely this item will ever get 'fixed', as blizz has probably forgotten about it, much like alot of the older content.

Having just got this, it may be changed now that WotLK is live.
My summon is level 62 at level 70. I was under the impression the summon would be level 60.

EDIT: At level 80, patch 3.0.9 the summon is still level 62. He does NOT scale with level.