Like anything, it depends.
Hapkido is a very good martial art, but it depends on what Hapkido you are learning and who is teaching it. Finding a good instructor in any art is better than what art you practice.
One problem I see with Hapkido is a lot of places that advertise Hapkido are just adding a few joint locks to what they already do and saying we do Hapkido too.
Hapkido schools, that do Hapkido only, are usually better programs and more complete. Hapkido is a complete art, not just something you add onto something else.
In a good Hapkido program you will learn to strike, kick, breath, fall, throw, tons of joint locks (what Hapkido is often most known for), weapons, etc. Probably the weakest area of Hapkido is groundwork, due to Hapkido's philosophy that you should put the other guy on the ground, but not be there yourself. (Very good philosophy for real fights, especially when the guy's buddies are around)
Hapkido programs do have some fancy more show techniques that you will see in demos, etc. However, there are a lot of practical self-defense skills that most students can benefit from in a fairly short time period.
Again, it really depends on who you are learning from.
Yours in Training,
Alain
www.burrese.com