Hello LynneB and welcome to mac-help
You have a really good point there ... it's taken a long time to get your mac set up exactly how you like ...
When I purchased my recent iMac, it came with OS 10.4.6 ... I loved and still love Tiger and when Leopard was released I didn't get on the band wagon. I read so many negative posts from people at various forums that there favourite apps were broken by Leopard but this is quite typical. Whenever a new OS is released, not every developer is up to speed with putting out a recent version of their software that will run the new Mac OS and really, even the Mac OS developers don't get it right first time. Usually it's not until Mac OS version 10.5.x is released that certain bug fixes are addressed.
It wasn't until Snow Leopard was released, and it wasn't straight away either, that I upgraded. The good part was you can upgrade from Tiger to Snow Leopard, leap-frogging Leopard altogether. That was sweet as was the cost ... a paltry $30 or so ... so I took the leap of faith hoping that some of the smaller 3rd Party apps I rely on would still work ... most did except for one I really can't live without (OpenMenuX) but thankfully the developer was on the case and I can still use the app ... phew!
Lion is pretty close to us now and it will also be very cheap to buy & who knows you
MAY be able to skip 10.5/10.6 in the upgrade if you have an intel mac ...
You really have to do the research first and whatever you decide, don't rush in ... wait in the wings and just watch the reactions of those who suddenly find their world crashing around them because their most needed apps aren't quite up to date yet.
Lastly, don't let anyone tell you you should update. It's your decision and eventually even they will have to opt out of the race to have the latest and greatest ... even I will too if a future Mac OS requires hardware that I either don't have or can't afford to buy ... who knows?
Personally I'm happy I upgraded to Snow Leopard. I saved a stack of money, was able to immediately benefit from a much stabler OS than Leopard and honestly, I can't say that Lion is offering anything that captures my interest ...
See me in 2 or 3 years ... then I'll know all about Lion and maybe it's successors?