Friday nights are pretty busy at Taka's, especially around 7:30-8P. If you want a seat at the sushi bar, I would suggest going around 6:30. Like the previous poster said, it's unlikely that you can 'reserve' spots at the bar. That said, once you sit down at the bar, you won't be rushed. I've been going there every month since they opened and have never felt rushed by Taka or any of his sushi chefs. The staff is super nice and always helpful.
I think it's hit or miss. The sushi bar is pretty small. We've never had to wait very long though, maybe 10-15 minutes at the most. Their sushi bar isn't conducive to lingering so I think there's a high turnover. Maybe give them a call and see if you can reserve the bar, but I doubt it. Sorry that I couldn't be more helpful.