Pros:
- No more this or that [ Wingborne Storm or Wilding Claw both are in your arsenal]
- Armor and Magic Resist "BURN" ;see Malady and Black Cleaver = 24 less Magic Resist and 45 less Armor.
- Extra Magic Damage with "EACH" attack ;see Malady and Wit's End
- High damage output early and late game
- Decent Armor, Magic resist and high Dodge rate.
- Extremely fast attack speed
- YOU CAN DANCE! and it gives you more Dodge rate! yahoooo...


Cons:
- A little squishy at 1 vs 3/4/5 [usually gets a double kill at 1 vs 2]
- No regen items [this is where Iron Mantle comes in handy]
- Average HP and Mana
- No crits

End Game Items should be Ninja Tabi Wit's End Rod of Ages Malady Black Cleaver [Luxury Slot]

Ninja Tabi - Dodge and Armor
Wit's End - Attack Speed and Magic Resist + Extra Magic Damage
Rod of Ages - Growing Health, Mana and Ability Power + level up heal passive
Malady -Attack Speed, Ability Power + Extra magic damage and Magic Resist "BURN" passive
Black Cleaver - Attack Damage and Speed + Armor "BURN" passive

Now for the Luxury slot choose any of these situational items that might be useful, It's actually "COMMON SENSE". Choose what you think you're lacking.

Aegis of the Legion Guardian Angel, Trinity Force, Hextech Gunblade, Frozen Mallet, Guinsoo's Rageblade, Warmog's Armor, Thornmail, Madred's Bloodrazor or any other item that suits your current gameplay.

Simple.
Why Ability Power? - Udyr deals extra Magic Damage with Wingborne Storm and it also affects Iron Mantle shield absorption. With your INSANE attack speed. The extra Magic Damage from Wingborne Storm will proc like CRAZY.

Why Attack Damage? - Common sense, Udyr is an extremely fast AUTO-ATTACKER. Malady Wit's End and Black Cleaver provides Udyr 120 Attack Speed, 55 Attack Damage + Magic Resist/Armor "BURN" + extra Magic Damage on each attack.
I'm not really sure how these items Malady Black Cleaver procs with Wilding Claw coz as I've heard Sword of the Divine extra Magic Damage procs only once with Wilding Claw [probably because of balance]. But surely, these items work on "EACH" attack if you pop Wingborne Storm or any other stance.

Rod of Ages will also provide Udyr what he's lacking "Health and Mana" and it's growing every minute.

Wilding Claw - pretty good at endgame especially at pressuring/destroying towers

Iron Mantle - a life saver if used wisely, also useful while farming and regenerating both HP and MP

Blazing Stampede - chasing, ganking, escaping, farming, CC'ing

Wingborne Storm - very useful combined with every stance, it also makes you a killing machine.

Start jungling wolves at level 1 then ghost if you have at least level 3 of Wingborne Storm
then lane a little bit for a gank or tower def. At level 3 Wingborne Storm farming will be a breeze.

You can kill the Golem at level 4 if you already have Ninja Tabi
Iron Mantle and Wingborne Storm is great against the Golem, dont forget Smite.
Why Golem Buff? - it's because it provides you fast mana regeneration that you need while farming and creeping, if you have this Aura you won't have any problem at Stance Dancing. It's also easier to kill the Lizard with this buff on, - just dance.

Smite - farm, use this whenever you can, or when farming Golem or Lizard
Exhaust - gank, anti-escape, purge

Other spells that might tickle your fancy :
Flash - escape, chase, surprise, gank
Teleport - DEF, creeping and most of all "IF YOU HATE WALKING"