I'm going to choose to ignore BoingBoss's post and move straight into my impressions so far. I am in no way a developer, so this all comes from a User's perspective.
The system is very stable. So far, I have not any any lockups. I've had a few Guru's caught by the GrimReaper, but the system stayed up. Reboot time is on par with, maybe slightly faster, than my A4000T. It's slower than my A600 and A1200 because those are essentially out-of-the-box OS3.1 and OS3.9 installs (there's nothing to load that would lengthen boot times).
CD drivers are now integrated into the system, like on the CD32, and CD drives are now bootable without any extra software tricks. Unfortunately, this means that if you leave the prerelease CD in the drive during a reboot, you'll be greeted with the Locale prefs and will need to pop out the CD and reboot once more. There are no longer CDx icons in DEVS:DOSDrivers. There are some CDRW/DVD+/-RW icons in SYS:Storage:DOSDrivers, but I'm not sure what they're for. My best guess is that they're part of the MountRanier CD-as-Floppy-type-device package.
I circumvented the IBrowse prefs problem by downloading the new Preferences immediately after installing IBrowse. I was a little upset by the fact that the default Icon installed for IBrowse was from MagicWB, but it was easily replaced with one from the CD (It looks just like the Icon for SYS:Internet under WB3.5/3.9)
Speaking of Internet, I'm quite confused by RoadShow. SYS:Internet on OS4 contains icons for "New Connection," 'Open Connection," and "Edit Connection," and no documentation (that I've found). New Connection brings up a Wizard to create a net connection, Open Connection brings up an ASL requester for files with a #?.conn pattern in an empty subdirectory (I haven't figured out what this is for yet). I eventually got something out of New Connection, but an output window appeared telling me that it had failed. A ping command from the Shell said otherwise; I'm now posting this from IBrowse in OS4, but a lot of network protocols don't seem to be working: I can't get anything from Aminet and I can't access my router. Getting Samba running is days away, at best. There's also a docky that's supposed to allow you to go quickly online and offline, but it doesn't seem to do anything. AmiTradeCenter doesn't work either. It gives a requester saying "Cannot open [garbage text]" and sometimes Gurus. I'll be investigating this thoroughly, as I had intended to FTP all my important files from my A4000T to my AmigaOne
In terms of bells and whistles, resolutions below 800x600 are complete garbage on my Radeon. It may be my crummy monitor, but I suspect this is the not-completely-fixed bug with the Radeon driver that caused the prerelease's delay earlier this year. I'm not too fond of the default OS4 Theme - Red text on a nearly-white background in all Reacation requesters isn't very appealling to me. I never used VisualPrefs or FullPalette much in the past, so adjusting to the OS4 GUI prefs and controls will be a bit tough for me. As a suggestion: A small preview window to show what the configured GUI looks like (so there's no need to hit "Use" every time you want to check something) would be nice. There's a preview button, but it doesn't seem to do anything. I'd also like to see an Iconify button built into all Workbench windows, not just certain Apps. There's an iconify commodity on the CD that can force a window to Iconify with a keystroke, but something clickable with the mouse would be nice.
As others have mentioned, the Workbench title window is now quite customizable. You can display free RAM, the OS version, the Processor installed, your GFX board, or even make it quote the first few lines of Hamlet, if you want. It's quite boring by default - the same as in OS2.x+, but it looks especially strange to see emulated Chip RAM in identical quantities with Fast RAM. Some improved defaults would be nice - like the ones in IntuitionBase's tips section.
I have 512MB of RAM in my AmigaOne, and about 124MB displayed on bootup. That means that OS4 is far more memory intensive than I thought, or it's not quite reporting things correctly. Still, that's more RAM than I ever had in my Classic machines, and I've got well over half a gigabyte free if virtual RAM is included.
ENV: is completely different with OS4. No longer is it a subdirectory of RAM:, but an entirely new device on its own, like RAM:, PAR:, or SER: from the Classic era. This had me very confused for a while, and I even went as far as to add Makedir RAM:ENV commands to my Startup-sequence (they're gone now).
MUI is installed by default, and is fully PPC native with a new Prefs program (It's slightly more user-friendly now). The option to dock menus with MUI windows (like in MorphOS) is present as well. There's also a new option to add a Screen Jump button to the titlebar of an MUI window. It was a bit bizarre to find MUI and ReAction/GadTools configured completely different in terms of appearance - I had expected they were to look similar. Maybe in the full release? I recall reading something about a way to quickly configure MUI to the ReAction look, but I don't really remember.
I haven't really tested anything CPU intensive to check speed yet, but the system is responsive, and the emulated P96 is faster than my CV3D under CGX in Zorro3 mode with an 060 for use in Workbench/IBrowse, etc. Blanker seemed to choke a bit, and that had me worried. Blanker now has monitor powersaving functionality built-in.
OS4 is the most difficult from-scratch Install I've ever had to do on an Amiga - there are a lot of staples from the classic era that are missing. There's no ShowConfig, and no LhA (Unarc and xad/xfd are present, but I prefer the Click-m-Click method of extraction in DOpus4).
To close, my thanks and congratulations to Hyperion & co. for bringing this to market. AmigaOS is in excellent hands, and I know the bugs will be ironed out in time for the main release. Criticisms aside, this is AmigaOS, and if you haven't used a next-generation Amiga system yet, you won't regret it.
Oh, and for the record, my copy of the prelrease arrived in the mail at about 11:46 AM on Monday, July 12, from SoftHut.
