I have used 10.5.8 on my PowerBook G 4 (1.5 Ghz/1.5Gb Ram) for the past 3 years. I bought it used and it had 10.4.x installed which I upgraded with my Leopard retail DVD. There have been no performance issues and I am using Safari 5.1.5 presently.
If you want to go the clean install route I suggest you consider an external bootable firewire drive (SuperDuper or Carbon Copy Cloner) to clone your present HDD to. You can then boot from the external clone drive and wipe the original drive then install 10.5 from the DVD. Finally you use migration assistant to get all your stuff from the external clone onto the PowerBook.
If for some reason you do not want to keep 10.5 then you can clone the external 10.4 back to the PowerBook or use it as an alternate startup. If you are happy with 10.5 then use the external to clone the 10.5 installation as a backup ( a lot more reliable than Time Machine, IMO). Be sure to get a firewire external drive as USB will not boot G 4 PowerBooks
I purchased mine here; http://eshop.macsales.com/shop/firewire/on-the-go
If you're looking in the used market, make sure you look at retail versions and not gray-faced disks, as the gray-faced disks are locked to the systems they were delivered with (and Powerbooks never shipped with Leopard).
You can buy new unopened Leopard software from http://www.hardcoremac.com
I've run Leopard in my PB 1.67Ghz with 2GB memory for a couple of years with no issues I'd call out.
Thanks dalstott and BGreg for your response, which are both greatly appreciated.
It is good to know that you have both been using Leopard and it seems to be stable. I have just also ordered additional ram just to take my powerbook up to the maximum 2GB, as I figured it can't hurt!
With regards to doing a clean install I'd actually prefer not to and would like to know is that fine to not do so?
Thanks for confirming that it is the retail version that I require. Can I purchase the Upgrade retail version seeing as I already have tiger on my machine? Or do I need to purchase the full retail version? I am based in the UK so will firstly try to purchase from a UK based seller firstly, such as Ebay, but many thanks for the links.
Any additional help you or anyone else can offer would be appreciated
There is an upgrade disk for Leopard which requires 10.4 to be installed ... this is what I used. It works fine, unless you need to reinstall it after you do the upgrade ... no more 10.4 on the system so it will no longer work! That may be OK if you have good backup, just be aware of that limitation.
When you upgrade, you need to look at any programs under login items under your user ID as well as any programs listed on the System Preference pane, to see if they need to be upgraded to Leopard in order to run. Also go through your applications list and look at the non-Apple applications to see if there is a Leopard upgrade available for any of them.
Mac OS X 10.5 Leopard installation system requirements
Leopard is no longer available at the Apple Store but may be available by calling Apple Phone Sales @ 1-800-MY-APPLE (1-800-692-7753).
If you can't obtain a retail install DVD from Apple, look on eBay or Google the installer part numbers to possibly find at an on-line store. Here's what to look for:
MB427Z/A Leopard 10.5.1 install DVD
MB576Z/A Leopard 10.5.4 install DVD
MB021Z/A Leopard 10.5.6 install DVD (single user)
MB022Z/A Leopard 10.5.6 install DVD (5-user family pack)
Installing Mac OS X 10.5 Leopard
Mac OS X 10.5 Leopard Installation and Setup Guide
After you install the base 10.5, download & install the 10.5.8 combo update at http://support.apple.com/downloads/Mac_OS_X_10_5_8_Combo_Update
The DVD should look like this
Caution - Leopard does not support classic mode. So, if you currently open OS 9 apps in classic mode, you won't be able to do this if you upgrade to Leopard.
Thanks BGreg and Texas Mac Man your advice has been invaluable.
BGreg:Thanks for pointing out what to bear in mind should I purchase the retail upgrade version!
Texas Mac Man: thanks for all the links you have provided and for part numbers to look out for. I found one out of many on ebay but the part number is as follows:- MB0212/A, but was not listed by you. Is this version okay? As the seller says that it is the full retail version also.
Guys I really appreciate your help and if you think there is anything that might be helpful then please let me know.