I'm significantly worse in my job than what I remember from before I had kids. What I miss most was the "deep thinking" mode that I used to get into, when you think about a problem for days on end, and solutions and ideas start popping in your head while you're in the proverbial shower. This rarely happens to me nowadays - the life I have outside of work scrubs my mind clean like a metal brush the second I step into…
I'm not sure if I'm significantly worse in my job since I've had kids (I have a two and a half year old boy), but what I'm not able to do is keep up with "the kids" who get to work at 8:30 AM and leave at 7:00 PM, because they're young and single and no one is waiting at home for them. I try to leave at 5:45 PM so I can get home in time to help out with dinner and putting him to bed.
So many folks I work with get home after their kids go to bed. I just don't want to miss all that time with my son. It's definitely affecting how I'm perceived at work, because I'm seen as not as "dedicated" as the folks who stay at work till all hours and are online late at night at home. It's constantly striking a balance between the demands at home and the demands at work.