Manual mode DSG is no replacement for a normal manual gearbox. Ultimately, a computer is still deciding if you can actually shift when you click the paddle, and will override you if it isn't happy.
Sometimes, it will get confused as it will expect you to go up/down, and then you ask it to do the opposite, and there is hesitation while you wait for it to sort itself out.
DSG is a compromise solution that lets you feel like a bit of a racing driver, and makes the daily commute and sitting in traffic more much tolerable, but it isn't the same level of control or 'connection' to the drive.
You really need to give it a decent go to see if it for you. I went from DSG to a manual a few years ago and missed the extra control the manual gave you, but as it was my one car to do it all, the commuting sucked and I went back to DSG for my Leon.