Looking through Softpedia Windows downloads I ran across Mustang Browser
It is based on Chromium. But the flash player works out of the box. Also it seems to have built in settings to limit the number of exe instances. Starting up with a blank page it shows 4. With 6 tabs open it shows 6.
So far i've installed Fastdial and Vanilla Cookie Manager. It comes with AdOff already installed.
So far so good. It has the dialog to import bookmarks and settings just like chrome.
My first impression is it is chrome with a sanity check on the number of running instances.
Edit: I posted the Softpedia download link because the file seems to be hosted with the download servers. The home page listed for the program is a commercial consulting site with no link to any freeware I could see.
Edit2: There seems to be no portable version. Note that the installer is quite primitive. You click install and it puts the stuff under Program Files (x86) on a x64 Windows and makes itself the default browser. It also adds a button to the Taskbar. Just so you know what to expect.
Edit3: It is not as super snappy as regular chrome but it seems pretty stingy on memory. See screen shot.
Edit2: I found a lag when opening new tabs. It seems to wait until you click the tab to load. What it turned out to be was Fast Dial. It was set to load a background image on the new tab page before loading dials. There is still a bit of a delay when clicking on a new tab where the background is white. But the delay is much less noticeable if the Fast Dial has this option set to off. I noticed complaints about slow tab loading for chrome generally and the answer seemed to be to check an extension that manipulates the new tab page.
It seems very usable now. Looks pretty nice with Vista Aero Theme.