Yes, it is a bit heavy on CPU, but remember how much processing is going with it. As for the other issue...I haven't run into that at all. You might mention it on
the Serum forum on the Xfer website. Steve Duda is pretty good about responding to any potential bugs.
One really nice feature he has it that for automation, there's a complete list of all the knobs with the automation menu in the VI window so you know exactly what's what when setting up an automation lane. There's so many, that just use numbers and you can't label them!
I know there are already some pro sound developers getting ready to offer up some new sound banks for Serum in the next month or so.
This a great overview video of Serum from Plugin Guru John "Skippy" Lehmkuhl.