4 months post hair transplant - growth slightly uneven, is this normal?

Yes, it's very common for the hair to grow at different rates after the procedure.  It may take up to 18 months for the hair to be fully grown and then you can determine if you need more grafts to fill in areas that didn't take.
Thank you for your question!
Dr. Schreiber, Baltimore plastic surgeon

At this point it is difficult to comment on the final result.It is not unusual to have early uneven growth-full results will be evident at one year.