I've been using conky for about a week now, and I kept noticing that it would use approximatly 1-5% of my cpu quite frequently. Not that I don't have the cpu cycles to spare, but that seemed a little goofy. I messed around with the .conkyrc configuration file but it still seemed to take up a bit too much of my cpu.
Falling back to my days of Gentoo, I decided that the best thing to try would be to build conky from source. Here are the steps I took on Ubuntu 8.04 amd64. First I downloaded the source, this should be done from conky's website. I downloaded the latest version which is 1.5. Then I extracted the source file I downloaded the .tar.bz file so I used the following command.
tar -xjf conky-1.6.0.tar.bz2
I then moved into the directory created using cd
These are the configure options I used.
./configure --enable-wlan --enable-nvidia --enable-rss --enable-network
Conky's configure is excellent, it runs quickly and gives you a list of all the options that have been enabled. Review this file and be sure that everything you want conky to be able to do is enabled.
Then run the compile
sudo make install
There you are done and you should find conky runs smoother on your system. Of course this isn't guaranteed but it can't hurt.