Is a 1/2 bad on my first NCOER?

You need to look at where the 1 and 2 fall in the rating , both are still successful and superior. For a first NCOER that's not bad at all, I think your rater did you justice by letting you know there is room for improvement.
One common mistake for many raters is giving someone 1/1 when they don't truly deserve it and the rated NCO often items feels they are on track when in reality they need to improve somewhere. Then the next rater gives a lower more realistic rating and the NCO feels slighted.
A 1/2 is good even a 2/2 would be good for a first time report.
Think about who you are rated against, it's not the entire Army. If you are a squad leader you are compared to the other squad leaders in your platoon. A competent rater knows that out of three or four squad leaders they rate only one can be among the best, that's your competition.

SSG (Join to see) - the purpose of the NCOER is to help you see yourself - your ability to perform and improve yourself, your organization and your peers/subordinates.

Honestly, the Sr Rater portion ratings - the 1/2 you speak of, are totally irrelevant in your situation - you are a young SGT and this NCOER will be so old by the time you get looked at for SFC, that they won't even go back that far. Additionally, the Sr Rater portion is not going to be what gets you recommended to go to the SSG board - your performance/potential is.

Focus on what your rater says you are doing well and the things you need to improve on - that is the benefit to the NCOER.

Whether or not a 1/2 is good or bad is irrelevant.
What you should be asking is was the 1/2 and accurate evaluation of your performance and potential. There are many things in the Army that you have no control over, but your NCOER is NOT one of them.
Your actions, attitude, proficiency etc. combined with COUNSELING from your rater (and remember, the quarterly counselings are MINIMUM requirements) will set the stage from your evaluation.
If you really want to stay ahead of the game, ask for more frequent counselings, ask questions on where you can improve, set tangible and measurable goals. Do this and you should never be surprised by your NCOER.