the best part is the sense of wellbeing. Definitely more confident and in control. It's great. Can work out longer in the gym. when you normally are getting tired in the gym, you all of a sudden have a second wind to work out more.
Libido increase. Not just morning wood, but random wood throughout the day.
Everyone is different, but I think if you are naturally aggressive, test will amplify that but not "roid rage". If you are assertive, you'll be more so. If you are the quiet confident type, you won't become a prick all of a sudden.
The final thing is more test in your body may "tip the scale" in some confrontations. For example, if you usually say, "Fuck it." to yourself and walk away, you may find it easier now to say (aloud), "Fuck you, you prick!", and deal with the issue that way.
Which way is correct? Up to the individual, but the scale tips to directly dealing with the situation. That's been my experience on increased test.

Yes, you will feel like a superhero and no, you won't be any more irritable unless you were already a jerk without the steroids.

One thing I did feel and didn't comment with anyone is how real everything felt while on test. The middle and last weeks I had a very strong feeling of "Wow, this is really my and I'm awesome". I admit I even got a little emotional sometimes but not in a "boo, I'm gonna cry" way, more in a "THIS IS FUCKING REAL" way, if that makes sense.