What is the life of an Infantry Officer like (starting from 2LT)?

Modern Infantry Officers are significantly different than infantry officers of the 19th century and earlier. Since WWII started infantry officers included light, airborne, mechanized, motorized, ranger, and mortar SGT (Join to see)
My experience as an infantry officer goes back to 1980 when I went through the Infantry Officer Basic Course after going through the Infantry Mortar Platoon Officers Course [for commissioned and non-commissioned officers] at Fort Benning, Georgia. A typical initial assignment is as a platoon leader in a light, airborne, mechanized, motorized, or mortar platoon.
I was prior military service and a USMA, West Point graduate. You need to leverage your own training and experience and be willing to learn from those you lead. Nobody is an expert on everything, after all.
Your 1SG and Company Commander will hopefully let you know strengths and weaknesses of your NCOs if you ask them. Generally most NCOs are dedicated professionals. I had to relieve a couple which was traumatic for them and me. Later in my career after IOAC and serving as company Commander I helped protect my NCOs from false criminal charges.
Stand up for you soldiers and generally they will stand up for you.

First, going from an NCO to officer, you're basically starting your career over. No one cares about what you did enlisted unless you got a badge or a tab for it. The Army isn't like other services where they value and respect enlisted experience. Second, PT your butt off. It still escapes me as to why but the Infantry places more emphasis on your running ability than anything else. If you can run, you're a stud. If you're slow, you suck, no matter what else you can do. Push-ups and sit-ups don't seem to matter as long as you pass them but you'd better be able to run. I had 18 years enlisted time when I commissioned so I was 39 in IOBC. Running in the low 17:00s was normally pretty respectable for a guy my age but if you aren't running 15:00, don't even bother. Personally, I've always felt that running was a poor substitute for good marksmanship but the Infantry school vehemently disagrees. I've personally never had to run in combat (a virtual impossibility with 85 lbs of crap on you), much less 2 miles in 15 minutes. Third, EVERYTHING is about the "Ranger Standard." They will tell you 500 times that IBOLC (or whatever they hell they are calling it now) is NOT pre-Ranger school. It isn't. It's pre-pre-Ranger school. Fourth, once you make Major, nobody cares what branch you are. The Army will put you wherever they need a field grade body and tell you to figure it out. You will have to politic for battalion S3 and XO positions so that you will be qualified for battalion command. Complete ILE/AOC as soon as possible or you'll be behind the curve. If you don't have a Master's degree get one, MBA preferred. Make no mistake, very few Infantry officers make it into battalion command. Most retire as O-4 or O-5 without command due to huge reductions in combat power over the last 2 decades. Infantry is the most requested branch by all commissioning sources and is EXTREMELY competitive throughout the entire career path. Badges and tabs are your friend there. I met a 2LT in MLC at Benning who had been in Army schools since he commissioned and was getting sick of it after nearly two years but he was set until he was eligible for captain. One last piece of practical advice; get a reliable car. As an officer you will need to be punctual and reliable. A good car will help you with that. Buy two if you can because as the Special Forces guys will tell you, "One is none."

It is not bad. You will have a lot to learn. But career wise it depends. The biggest factor is if you are Ranger Qualified or not. This will affect your assignments. If you want to go to an Airborne unit you will have to be tabbed. Assignments will make your career. There are some units that will aid you in moving through the ranks. As a leader you will be expected to perform at a very high level. For your sake the Army will give you an SME. Your Platoon Sergeant will make you or break you.