it's actually true that ettercap makes the connection horrible when using it on N900

that's why i have just finished uploading arpspoof (as package name dsniff)
which is already confirmed to not slowing down the connection as ettercap does especially when running heavy sniffs such as sslstrip and YAMAS script (Based on sslstrip)

soon this problem will be solved for N900 as arpspoof will be the dependency of yamas

and for N9
unfortunately i don't have one

so till i get one (maybe will never)
then i will port hacking tools to it

PS: ettercap re alive is awesome
will contact the author of the ettercap package to port it to N900 (it's very easy to do)