I initially went the upgrade path, then later decided to do a complete reload of the OS. Not due to any issues, but just to clean things up.
Same here - although I migrated all of my apps and settings back in after the clean install. I haven't had any stability problems either way.
Everything seems pretty smooth to me. Only issues are that i don't like the transparent menus and I'm not that impressed with stacks.
I like the transparent menus. They definitely made them more opaque since the original demo, and I think it works. Where I really agree with you is on Stacks. Here are my gripes:
1. Stacks need to have a foreground icon indicating the directory category (downloads, applications, documents, etc). Easily remedied with a few readily available tweaks, but still an annoying oversight.
2. Fan view is great, but I think it should "scroll". That is, if the directory contains too many items to display in a fan, it should allow you to scroll through the entire directory using the scroll wheel / two-finger gesture or arrow keys. Just seems like a natural thing to me...
3. Grid view needs some performance tuning. On my MBP, it's jerky and there's plenty of horsepower here that it should be smooth.
4. I'd like to be able to click and hold on a stack to have it display as a menu - just like it did under Tiger. It was nice to have a sort-of Start Menu like interface when I had my Applications folder on the dock in Tiger.
Also, I need to get a bigger external drive before I can take advantage of Time Machine. Everything else is all good.
Time Machine works fine, but I wish it had an "advanced" mode. I think the intent was to make for brain-dead backups/restores, but I'd like to have an advanced mode where I can control when the backups happen, and what type of backup it does (incremental vs. full). Just a thought....
Otherwise, my only other gripe with Leopard is slow boot ups. My machine no longer performs like it did under Tiger in this regard. I would give anything for the 15 second boot-up times that I used to enjoy.... in fact, I've thought on more than one occasion of going back to Tiger until they get some more of the bugs worked out.