Probably best to not characterize it as a martial art, though. You'll learn timing, joint locks and throws, sword, staff, and knife techniques, how to fall safely... but most importantly, how to clearly lead and completely follow, depending on circumstances. I've heard it phrased as "the study of harmony"--not just in physical confrontations, but in arguments, office power struggles, and hard life decisions. It's not necessarily a good way to beat someone up: maybe more of a way to resolve a conflict without so much fighting.
Aikido is frustrating because it might require 10 years to become good enough for it to be marginally useful in a fight. However, how often do you really get into fights? If you're an aikidoist, you've basically accepted that you're learning about a beautiful art form. If you want the most effective way to hurt someone, try Krav Maga.
If you are the sort of person who is attracted to complex, difficult ideas that make you re-evaluate everything, aikido may be for you.
Aikidoists also tend to be professionals. It is sometimes called a gentleman's martial art. (No offense to ladies.) You often encounter doctors and lawyers and artists so on. On the other hand, in any reasonable dojo, none of that matters.
As he grew older, post-WWII, his philosophy and style became much softer and more spiritual than the styles he studied in his younger days. This was due, in part, to his age (changing perspective and physical decline) and the influence of the Omoto-kyo. In these later days, the purpose of training with weapons were twofold: help students learn body dynamics and learn to defend oneself against an armed attacker. The purpose wasn't to be armed and gut your enemies, the purpose was to understand the mindset of an armed aggressor, know their movements, and meet their movements without being gutted yourself.
I've heard (second-hand) a story about a high-level practitioner who got to spar with O-Sensei and at times he felt like he might not survive.