Hi, 
Thanks for trying out Twistpad.
regarding your query's:
dandersahn wrote: 
1) can't use middle click to close tab 
 
Agree, this is pretty much a standard, so it will be done.
dandersahn wrote: 
2) can't do regex to parse tool output to jump to line in file
3) can't send selection and/or content of buffer to stdin of external tool (I know that the slection can be passed as an argument, but that is very limited)
4) can't replace current selection with the output of an external tool
 
This are all tool related, and some features you mentioned are not common in general purpose text editors. I will definitely see what are the options in implementing this.
dandersahn wrote: 
5) no macro language 
 
This is planned for future releases.
Sorry for being a bit vague, particularly about the tools improvements, but it's difficult to say feature x or y will be implement and I prefer not to make promises that could or not be happen in the future just to sell licenses. 
Thanks,  
André Santos  Carthago Software Support  
http://www.carthagosoft.net