If your machine is mission-critical: No.
If it's not mission-critical and you have another machine: Yes.
Half the reports of people who blame their problems on 10.3.5 had problems BEFORE 10.3.5, and since we're all trigger-happy to point the finger at the latest OS X point release, that's where half of these "10.3.5 hosed my system!" reports come from. If you've heavily modified your system, or haven't repaired permissions in the last 6 months, or haven't checked the integrity of the disk, or have mucked around in the terminal a whole lot, or changed a bunch of settings via the command line, then chances are you'll have problems when it comes time to apply a system update. That does
not mean that the update hosed your system --
you hosed your system by not keeping it in good health.
Take the number of bad reports of 10.3.5 you've heard, discard the ones that you read in forums or discussion boards, then divide the remaining number of reports by 4 and you'll have a rough estimate of the number of problems that 10.3.5
actually caused.
The only
real problem with 10.3.5 right now is an issue with single-processor G5 1.8GHz machines:
http://docs.info.apple.com/article.html?artnum=25810