I took the plunge an installed 10.5 on Friday, with mixed results, but a generally good overall experience.
First up - customer service-wise I was amazed - I pre-ordered it on Thursday via the Apple online store and had it in my hands at 10am on Friday morning. First big tick.
I made the mistake of doing a basic install first time around and ended up with a dead blue screen on restart. I must’ve wasted a good couple of hours running through what I thought may be the problem before succumbing to calling tech support. Again, customer-service was excellent. I was only on hold for about 10 minutes at 6pm Friday night, and the dude knew what the problem was straight away. Basically, if you’re a heavy user and have installed loads of fonts and peripheral extensions, 10.5 may not like it, and will just hang on start-up like mine did :-(.
The trick is, do an “Archive and Install” first time around and it’ll boot up no problems, saving the old system in an archived folder. You’ll then just need to reinstall fonts and any drivers for peripherals.
The UI changes are generally excellent - with things like Spaces and dock folder views nice time saving additions. The new Cover Flow view is also neat, especially if you work in graphics - and the Quick Look function is also excellent.
Auto-mount networking is also a nice addition so you can see all of your other computers in one hit without needing to search for them first.
The new build of Safari looks a lot more stable, and the addition of the Web Clip function to add page snippets to dashboard is great, but doesn’t seem to like anything that’s overly Javascripted.
Time Machine looks like it could be excellent, but you’d really need a separate drive with equal or double your main drive’s space to take full advantage of it - and it’d need to be on all the time to make use of Time Machine’s hourly backup.
Apart from that, there’s a load of other cool little additions, like video capture in Photo Booth, and desktop sharing in iChat that could make remote collaboration even easier.
Definitely seems worth the $150 at this stage, but it looks like my installation problems weren’t an isolated event… whoops.