Each new OSX version has some nice little new touches to them. However you also need to consider your machine & how it would cope with Leopard. My G4 733 which started with erm .. cannot remember if it was 10.1 or 10.2, but I'm leaving it at Tiger (another G4 also being left at Tiger). My new machine (a year old now) came with Leopard. Rumors are that Snow Leopard 10.6 will be out before the end of the year, possibly mid year.

It is a little disappointing that apple stop updates for earlier OSX's after a time. Java is the first one they stop.

As far as upgrading just for the sake of LW 5 is not a good reason. I can assure you LW 5 is not as good as LW 4 as far as experienced users are concerned. At this point, LW 5 is still missing many tools that LW 4 has. There's been many old & new users reverting to LW 4 even when LW 5 was their first experience at using LW. Perhaps by end of year LW 5 will be a decent program. But at present, it is CPU hungry, hates large amounts of shares or incomplete files & will be very slow loading & responding if you do have many. Difficult to know if this is due to LW's new development territory they're learning or OSX's Java 1.6. Apple make their own Java unlike windows & linux, & Apple's java has never been anywhere near as good. Some of their Java versions have had major memory leaks.

LW 5 dropped Chat & by sounds of it they will not be bringing it back in. They also dropped Direct Connect, which has more or less been replaced by Friends. There's already been problems with this option. Download slots have been reduced to 10. Simultaneous searches reduced (search tabs just disappear after you reach 10). At present cannot browse uploaders.

There might be some programs you need to update for Leopard, however in general Tiger is a great system. I wouldn't rush into Leopard quite yet.

My Leopard System folder uses up 3.84 GB, My Library uses 23 GB but most of that 16 GB is due to Application support which is for some very heavy graphic programs. At present system using about 1 GB ram for the system, but that might also be due to some other rather heavy applications using the system's resources, as well as their own ram.