I spent a few hours this weekend creating a SharePoint 2010 Developer environment using the RTM.
For now, I'm approaching my dev build the same way I had my MOSS 2007 VM set up - a standalone MOSS install with Visual Studio installed.
Because I wanted to use a 64bit guest OS (64bit Server 2008), I decided to use VirtualBox as my VM solution, if you want to use VirtualBox, you can get it here. I should note that when I set up my VirtualBox VM I gave it 20GB of hard drive space which was not enough so I had to expand the drive (described later orange text). I'd suggest going to 40 or more if you can because Windows,SP2010, SQL, and Visual Studio take up about 18GB (and setting it up right the first time will save you from having to do this.
Once I had Server 2008 installed on a VirtualBox VM I downloaded the RTM version of SharePoint from MSDN.
I then attached the SharePoint 2010 .iso file to my VM, opened the mounted SharePoint 2010 image and ran the Prerequisite installer (I got an error as autorun tried to run).
After the prerequisite installation finished, I ran the setup, entered my product key, and chose to do a Standalone install. (I might do a Farm install so that I can use SQL Server as my backend, but you need to use Domain Accounts if you want to do this and I haven't set up a developer domain yet).
I did run into one hiccup, apparently during the installation I got a BSOD (though since I walked away during the install I didn't see the details). Once the server came back up and I realized what had happened, I reran the installer and the installation finished successfully, however, the Configuration Wizard wouldn't run (I got a 'failed to start the database service MSSQL$SharePoint' error). After going to Control Panel, then to the Uninstall Programs screen, I chose SharePoint 2010 (this wont show up unless you finish the install after the Blue Screen) and then chose 'Change', and selected 'Repair'. After the repair, SharePoint asked for a reboot, so I rebooted.
Once the server came back up I was able to run the Configuration Wizard without the 'failed to start...' issue. The configuration wizard ran through its thing and finished successfully. To verify a successful install I pulled up Central Admin to ensure that SharePoint 2010 was indeed installed successfully. After being prompted for credentials, Central Admin came up.
*Next, I had to expand my Virtual Box VDI file. This process is documented here.
After that I tried to install Visual Studio 2010. I got through all the installer wizard screens but got an error upon the actual install, apparently the VS 2010 iso doesn't mount well in Virtual Box. So I took my VM's browser to msdn and downloaded the VS 2010 web installer. I ran the web installer and went to bed. I later returned to see that after .NET Framework 4's installation I needed to reboot. I rebooted the VM then reran the web installer and it picked up where I left off.
Next I moved on to SharePoint Designer, based on my experience with VS 2010 not installing from a mounted drive in VirtualBox, I chose to download the Designer 2010 code directly in the VM. I couldn't find it on MSDN, so I downloaded it here. The installation went smoothly without any issues.