Tried on VirtualBox 5.1. Very good overall. Looks nice and traditional 
Also I have tested all tabs of MATE Welcome - it is great and very user-friendly.
But I have some notes:
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It is strange that Minimal installation adds LibreOffice icon to the menu, but it does not function. It also does not start from terminal. I reported this to launchpad as bug 1813538.
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Software Boutique does not show applications with “Sorry, Welcome could not feature any software fot this category that is compatible on this system.” message. But it is expected, as 19.04 is not released yet.
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HPLIP is listed in Drivers tab of MATE Welcome, but does not show its menu in tray (it already known as bug 1810745.
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Unable to install Deja Dup from MATE Welcome (from Minimal install )- reported this as bug 1813549.
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In MATE Welcome two applications from Drivers → Software Utilities and Peripherals - OpenRazer and Polychromatic are not yet available for 19.04.The packages are now available for Ubuntu 19.04, thanks @lah7 & Luca Weiss. -
In MATE Welcome on Browser Selection - the Brave Browser does not install, but it is expected.
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As before keyboard LED indicator have low contrast on light themes.
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As before Caja does not show previews of text files on Bionic and newer versions.
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As before Human, Human-Clearlooks and other themes have incorrect gray window title color.
Fresh positive moment: I have added Ubuntu 19.04 (disco) to my PPA ppa:nrbrtx/xorg-hotkeys - so we can use Ctrl+Shift as keyboard layout switcher without problems (keys will be interpreted on release).