You probably won't notice anything that's worse, and you probably WILL notice a few things are a little better... and a couple things that are a LOT better.
Those couple things are the finder (tabbed finder FTW), the activity monitor (WAY more useful now), much better power management (a little to a LOT longer battery life, and less fan time at lower speeds; though they still don't allow granular control over sleep and hibernation. I use SleepLess for that), the slightly less irritating notifications; and the slightly to considerably lower cpu, memory, and power usage, in high overhead situations (when you've got lots of stuff open and idle in the background).
It also seems to boot a tiny bit quicker, and the virtual memory access patterns seem a bit better (my disk I/O indicators aren't flashing as much in low-medium workload situations). Scratch that... after a few hours, my virtual memory utilization is WAY better, as is my overall memory utilization and management.
Oh and multi-monitor setups are WAY better and more useful now, particularly if you're using an HDTV as a monitor.
I use Chrome and Firefox not Safari... if Google would make a native OSX 64 bit Chrome that would support appnap and sleeping idle plugins and tabs... that would be really nice. Until then... meh.
Also, iWork for free with new Macs.. cool I guess... I don't use it, again, can't give my opinion
Oh one bad thing...
On my wife's mid 2010 13" MBP the install was so slow, with so little feedback (it stayed at "about 7 minutes remaining" for over 20 minutes), that I thought it had frozen, and I restarted it. It turns out it was just in the middle of uncompressing a REALLY large file, and it took like 15 minutes to do so.
I figured it out because my early 2011 top end 15" MBP uncompressed the file in like 5 minutes and then moved on. So I started the install over on the 13" and watched the install log. I let it keep running and eventually it finished the install just fine.
Actually two things...
Downloading it sucked. It took 2 days to download 5 gigs, and I had to restart the download multiple times. Mac Appstore downloads in general are slow and glitchy, especially for apps over a few hundred megs.
Oh and a feature request...
Apple, next time include a free program... in fact make it an option in the installer... to create an installation USB drive or somesuch?
I have no problem donwloading a third party app (DiskMaker X works great), using a commandline hack, or extracting the install image from the app and imaging it onto a USB drive... but I'm a technology professional. Most people don't know how to do it, and they don't want to have to download 5 gigs for every computer they own, or when their computer dies have to download the OS again from the recovery console (allowing a reload from disk there would be nice too).
