Well then, let me be the first to tell you that I have returned to Tiger for MANY reasons.
Let me list a bit of my troubles for the casual viewer:
Here's my setup: PPC G5 Dual 2.3 ghz, 4.5 GB of RAM, 2 internal drives = 500gb, 1 external @ 500gb. All the RAM is from crucial and Apple - I've had it the RAM for over a year... so the freezes aren't related to old/bad RAM.
1 internal has Tiger the other Leopard (clean install). The external is for Time machine.
1. Several crashes (per session) of Safari
2. HUGE memory hog (here's the running programs: Finder, Safari, Firfox, ichat, itunes, iphoto, Dragthing, Entourage, ical.
a. Tiger - I would average 400-600 mb
b. Leopard - I run around 1800 mb
3. I've had a total system freeze (using MacPilot) whereby I had to hard restart.
4. While using spaces, I switch to a space where an app resides, only to not be able to bring up my last active window (not a frequent occurence -random.
5. I've had to restart a few times and when I did, I got a blue screen telling me to restart again!
6. Having my iphone plugged in when I start the computer - it takes 4-5 minutes before I am fully at desktop. (tiger is about 1 minute -these are general estimates)
7. Every time i restart in Leopard (not in Tiger), I lose my internet connection and have to restart my linksys wireless router (I'm wired in, my girlfriend is wireless)
8. Noticed not one "bit/byte" of speed increase so purported by the masses.
9. Horrible bandwidth hog in ichat video (yeah, I actually use it)
With that all said - I (personally) feel this is a SUPER DUPER STINKER!!! AND - I could be easily classified as a fanboi - check my sig and I've been on mac since day one of OS 9.1 with by beloved beige DT (gossamer) 266 mhz.
I was very excited by so much of this - spaces, time machine, new finder etc, etc. I tried to boot in tonight just to try again... I could never get on the web (after several router restarts) but Leopard just too beta for me.
I'll wait for the 260 mb 10.5.1 update before I venture deeper.
I know others who are backin' up a bit bacause of their issues as well. Apple better sort this crap out, or it is going to become fodder for the Vista vs. Leopard wars.
You obviously have a hardware issue that comes out when running Leopard.
There are some programs that just don't work with leopard yet, wait till they're updated.
As far as the Linksys router goes I had the same problem with one under Tiger, it used to drive me nuts. I finally replaced it with an Airport Extreme and have not had a problem since.
I now have Leopard on 5 computers Intel and PPC and they are all running flawlessly.
If all these problems were an issue within Leopard they would replicate them selfs on all machines or at least on some specific ones.
But from what I have read here and on other sites that's not the case, so logic would dictate that there are some pieces of 3rd party software and hardware that are causing the problems.
Definitely worth looking at from that point of view before blaming or chucking the whole OS.
Anyway, just a thought.