SMG isn't as smooth as driving a manual and can sometimes be a bit jerky if you go into a car park slowly / come up to a stop sign in second then need to drive off just as the car decides it needs 1st gear and puts the clutch in. I avoid this most of the time by hitting the - paddle / pushing the lever forward.
I've driven my car in auto mode for the best part of 2 minutes, hated it and have been driving it in manual mode ever since. It's much better. You can also get extended aluminium paddles off eBay for about $60 which make using the paddles a whole lot better.
I reckon SMG is pretty good in traffic in manual mode, obviously can't comment about auto mode. You get spoilt a bit not having to do the clutch work yourself when it's super boring in traffic.
As a tip lift off ever so slightly when changing gears. I mean the tiniest bit, still have a bit of throttle. This makes the shifts really smooth. I think S4 is the best shift mode personally.
Apart from that, enjoy the new car and get it to the track as soon as you can. It will make you appreciate the car much more, especially coming from what I assume is a slightly modified 135.