If you play online and use the PS Store, then you may wish to update. If you don't, then I would recommend holding off... unless you can think of another reason to update such as using it for DivX etc. Personally I wouldn't update a $400+ console to run DivX when you can buy a $40 stand-alone to do it or use the PC though.
Most sceners keep their PS3 Firmware as low as possible (1.50 or below), for no reason other than hoping a hole in one of the early versions will become public which will allow them to run PS3 homebrew and backups.
Additionally, most PS3 Devs are keeping their PS3 Firmware below 2.10 as that is the revision where Sony plugged the RSX hole. If you do update and can solder, consider installing an Infectus Mod to backup your PS3's flash first. Hope this helps.
if u keep the old firmware u wont be able to play the new games u have to update first in order to play theme
You wont be able to play online with your old firmware, but if you want to play without internet it will be ok to keep it. as far as i know even the new games does not require an update to play without internet
Should i update firmware 1.97 to 2.30 ? if there a benifit to keep old firmware?
in my personal opinion, until something solid in the hacking scene comes out and says that u shouldnt update then just update all u like, but only if you want the extra features, but if u dont just use ps3proxy found in the downloads section.