Too much overhead!

s/{.*\n//g;                  # remove lines starting with braces
s/(\\[\w-]+)\b//g;           # remove RTF commands
s/(\n)\s+(\S+)/$1$2/g;       # remove extra spaces
s/([^\\\n]+)\\(\n)/$1$2/g;   # get rid of \ at the ends of lines
s/\\\n//g;                   # get rid of lines with a \ only
[download]

Then execute with:

perl -0777 -p remove_rtf_formatting.pl < infile.rtf > outfile.txt
[download]