I have Ububtu Ibex (8.10), here's what I did:
1) Install the version of boinc that's available via apt-get (6.2.12). This provides a nice script that starts BOINC as a service at boot time, as well as the BOINC manager icon on my toolbar and in the "System Tools" menu. (package names boinc-client and boinc-manager)
2) Download that pesky .sh file from WCG, which is the 6.2.15 version, and run it, which unpacks itself into whatever directory you run it in.
3) service boinc-client stop
4) Make backup copies of all the /usr/bin/boinc* files (these are the 6.2.12 version files from the apt-get install)
5) copy the boinc* files from wherever you unpacked the .sh file into /usr/bin
6) service boinc-client start

I've been running with this setup for a couple of weeks, and the only thing that doesn't work are the buttons in the boinc manager that would normally pop up a browser (like "Result Status"). I can live with this -- I just created some bookmarks in my browser to go to these pages.