I had a fine motor skills problem from kindergarten to third grade and had to do extra work around that.  My parents didn't hold me back and I was so young I never associated any kind of stigma around the extra work.  I did just fine even though I had messy handwriting.  Does it really matter if a kid has messy handwriting in Kindergarten? Is there such a thing as good handwriting at that age? As long as he is able to understand the concept of writing and can learn to read well my personal opinion is don't hold him back.  Tell him if he doesn't clean up his handwriting he'll have to be a doctor when he grows up!

Kindergarten is about more than just fine motor skills. Does your child have difficulties in other areas? Since he is receiving services for his fine motor skills, I would check with these professionals who know your child's strengths and weaknesses. Then decide what to do. Often little boys are much more immature than girls at this age.

My daughter turned 5 on the same day as your son and suffers from similar issues.  We are in OT for fine motor but the improvement is very, very slow.  I have her in private kindergarten that is full day.  They feel she is behind in some areas.  I just had her evaluated again and she is still behind.  I don't regret sending her to kindergarten but I do worry she is not improving fine motor still.

Since I asked this question we did decide to send him and so far he is doing well and no there are no other delays.  He has been in OT for 8 mos. and his OT is considering discharging him.  Whether this happens or not I plan to continue working w/ him on fine motor skills, as will his Kindergarten teacher & wrap around teacher.  

As for the person who has the daughter the same age, a lot can happen in a year!  I know you mention that it has been slow, but this can definitely change.  For my son, it was the teacher and myself that really made the difference. With only 1/2hr. of OT/wk., that definitely wasn't going to cut it for him.  Best of luck to you and your daughter.