What are the advantages and disadvantages of becoming a werewolf?

While in regular form, there isn't a whole lot of difference between werewolves and non-werewolves, but when you transform, you get a ton of benefits and drawbacks:

Benefits

• Increased max health by 100 (non-regenerating)
• Increased max stamina by 100
• Faster sprint speed
• Wolves no longer attack you
• Committing crimes in beast form don't count against your normal form
• Immunity to all diseases, including vampirism (also cures vampirism if you have it)
• Special, werewolf-only abilities like howls

Drawbacks

• No looting (when a werewolf)
• No inventory or equipment access (when a werewolf)
• No talking (when a werewolf)
• People either run away from you, cower, or attack you (no friendly humanoid NPCs) (when a werewolf)
• If someone sees you transform, it's automatically a crime
• No rested bonus
• If caught transforming in public it's 1,000 gold bounty to pay

You can become a werewolf once per day for a couple of real-time minutes. It's excellent for serial killing of low-to-medium-level humanoids (like the Markarth prison), or for the fun of causing a major crime if caught transforming in sight.

When you have the beast blood, you cannot get diseases. The only disadvantages are that you can never get the "restful sleep" bonuses, and you are doubly vulnerable to silver weapon attacks. So I recommend that you get the beast blood through the Champions quest chain in Whiterun unless you're going straight through the main quest.

IGN's wiki has a good breakdown.

From this page, I can only find one drawback besides the fact that once you are in beast mode certain companions might leave you, and most people will react negatively to you being a werewolf. That drawback is that you cannot use the Rest buff after sleeping, which normally gives you a 5% boost in leveling up skills for 8 hours. It doesn't seem like different classes react differently to becoming werewolves.