OTHER RSYNC BASED SOLUTIONS 
and why I did not use them (some of these might work better in 
situations other than ours. YMMV)

rsnapshot - http://www.rsnapshot.org/links.html
* not organized by date.  rotates backups with index numbers.  
* lack of flexibility.  changing # of backups based on disk size only
  * other criteria such as date may be difficult to do
? perl based

rdiff-backup - http://www.nongnu.org/rdiff-backup/
* VMS style format for data storage.  not date organized.  
* pain to delete files older than given date (code handles it for you but i'd rather not deal with it.)
? python

dirvish - http://dirvish.org/
* wants to backup entire system tree.
* not efficient at selective backups and a real PITA to setup said functionality
 * ie I want to backup /root,/etc,/home but it wants to backup only one of them or the entire tree /
 * to get it to limit to just those directories I must use complex include and exclude rules
* Has issues with regression testing and maintainability
 * perl based - code is a mess.  no use of strict, etc.

ccollect - http://unix.schottelius.org/ccollect/
* The interval between backups specifies how many backups are kept.  # of backups and interval between should be distinct

rlbackup - http://www.math.ualberta.ca/imaging/rlbackup/
* not centralized.  requires too much configuration on client

rsync-backup - http://www.stearns.org/rsync-backup/README
? runs in chroot.  requires setup
* uses client setup to push backups to server.  (Dangerous! according to INSTALL file--and I agree)
 * not centralized--for security reasons?

boxbackup - http://www.fluffy.co.uk/boxbackup/
* not centralized.  requires configuration and daemons on client

backuppc - http://backuppc.sourceforge.net/info.html
* incremental backups may not be 'accurate' for smb and tar
* rsync does not handle backing up hard links properly (not a big deal maybe?).  
? perl based

rvm - http://rvm.sourceforge.net/
* written in C.  must compile program (why?  it's just a wrapper around rsync.)
* large amount of complex configuration directives. 
* everything is in one big config file?  in fairness you can use includes to keep things in separate files