This is some notes on how we upgrade from SA 2.6 to 3.0.

Upgraded to using Razor Client v2.67 without issue (and without requiring the taint patch)
cd /files
wget http://www.peregrinehw.com/downloads/SpamAssassin/razor-agents-2.67.tar.gz

# Install Razor Agents v2.67
        cd /usr/src
        tar zxvf /files/razor-agents-2.67.tar.gz
        cd razor-agents-2.67
        perl Makefile.PL
        make
        make test
        make install

	#Create a Razor Client Identity 
	#NOTE: Sometimes it puts these in /usr/local/ but I haven't figured out why...

	/usr/bin/razor-client
	/usr/bin/razor-admin -create
	/usr/bin/razor-admin -register   #... Repeat register until successful

#Upgraded to newer Net::DNS
cd /files
wget http://www.peregrinehw.com/downloads/SpamAssassin/Net-DNS-0.48.tar.gz

#Added Net::Cidr::Lite
cd /files
wget http://www.peregrinehw.com/downloads/SpamAssassin/Net-CIDR-Lite-0.15.tar.gz

Added Sys::Hostname::Long
wget http://www.peregrinehw.com/downloads/SpamAssassin/Sys-Hostname-Long-1.2.tar.gz

Added Mail::SPF::Query
wget http://www.peregrinehw.com/downloads/SpamAssassin/Mail-SPF-Query-1.997.tar.gz

#Not Running Perl 5.8?  Maybe you need Storable:
#wget http://www.peregrinehw.com/downloads/SpamAssassin/Storable-2.13.tar.gz

#Installed SA 3.0
cd /files
wget http://www.peregrinehw.com/downloads/SpamAssassin/Mail-SpamAssassin-3.0.2.tar.bz2 
wget http://www.peregrinehw.com/downloads/SpamAssassin/spf-spamassassin-3.0.2-patch

cd /usr/src
tar jxvf /files/Mail-SpamAssassin-3.0.2.tar.bz2
cd Mail-SpamAssassin-3.0.2/
patch -p0 < /files/spf-spamassassin-3.0.2-patch        

#Create a database called spamassassin

#CREATE THE DATABASE TO STORE USERPREFS AND CONFIGURE SPAMASSASSIN TO USE IT
/usr/local/mysql/bin/mysqladmin -p<Root MYSQL Password> create spamassassin
mysql -p<Root MYSQL Password>
GRANT ALL PRIVILEGES ON spamassassin.* TO spamassassin identified by '<db password>';
quit

#ran make test, got lots of errors.  Figured it doesn't make the tables automatically
#
#Fixed by adding the tables. Used the default tables that SpamAssassin includes SQL format information to create:

 mysql -p spamassassin < /usr/src/Mail-SpamAssassin-3.0.2/sql/bayes_mysql.sql 
 mysql -p spamassassin < /usr/src/Mail-SpamAssassin-3.0.2/sql/awl_mysql.sql
 mysql -p spamassassin < /usr/src/Mail-SpamAssassin-3.0.2/sql/userpref_mysql.sql

#Fix the Atime Index (thanks to parkerm for the better index)

 mysql -p spamassassin 
 alter table bayes_token add INDEX bayes_token_idx2 (id, atime);
 exit;

#ran make test.  failed on spf stuff but looks like possibly a bad test.  It is noted in bugzilla:
#  http://bugzilla.spamassassin.org/show_bug.cgi?id=4044
#
#Patch to fix most of the test issue:
#  patch -p0 < /files/spc-spamassassin-3.0.2-patch 

perl Makefile.PL
make
make test #Sometimes have to run more than once
make install

For MIMEDefang, I've edited the /etc/mail/sa-mimedefang.cf (and deleted other local.cf and sa-mimedefang.cf in /etc/mail/spamassassin).  I then modified my mimedefang filter minorly:

use Mail::SpamAssassin::SQLBasedAddrList;
my $awl = Mail::SpamAssassin::SQLBasedAddrList->new();

This allowed me to use the AWL via mysql.  I know DB, etc. might be faster but I like mysql's stability and ability to run 
without negatively impacting server performance unexpectedly.  Seems to be working fine so far!

NOTE for those using SPAMD/SPAMC & Procmail: I use SPAMDOPTIONS="-d -m2 -q -x -u spamd"