It takes practice but I can easily granny shift with A/C on often at 1500-2K.
If you want to take off fast you need to get your RPMs up before letting the clutch up, and even ride it a little, something I hate doing but sometimes it's necessary.
When shifting normal you need to give it more throttle and let the clutch up slower but you can shift smoothly with some practice.
What's really fun is when your fan is on slow and its cool out so the compressor cycles constantly. It's like a lottery, will I shift when the compressor is on or off?
And that is why I hate the fact GM put a fixed displacement compressor in the Sonic rather than a variable.