There are two aspects to consider - how well the Mitsubishi XL1550U - and XL2550, by inference, do with business presentations, and how well they do on video.
Let's start with normal business/education/government type uses - which normally means Powerpoint presentations, spreadsheets, email, word documents, assorted charts, diagrams and photos.
As you can see from the color bar chart here, overall, colors are very good, with both primary (red, green, blue) and secondary (cyan, yellow, magenta) all looking very reasonable. This differs dramatically from most DLP projectors which tend to suffer from bright reds that come out dark, wine colored, and bright yellows that come out sickly yellow green.
Here are a couple of other screen shots, to demonstrate the XL1550U's color handling. Please note, these may look just a little washed out. This is due to taking the pictures with full room lighting with four overhead 70 watt recessed lights in a small room and some outside light coming in one window, the screen size in use, was approximately 88 inches diagonal. Not a huge screen, but a fairly large screen for a conference room, or training room:
Note, the border to the left and right of the projected image - what you are seeing there is unused portions of the screen. The lighting in those areas appears very dark, but that is due to the exposure being set to capture the presentation properly. In reality those sides were rather bright from the rooms ambient light.
In fact here's another shot of the room, with the metering on the camera set between optimal for the presentation, and for capturing the room lighting. As a result, the presentation itself is badly washed out - overexposed, but it does give you a decent idea of how the room is lit. This isn't as bright a room as one with full florescent lighting and white walls, but it is still definitely a bright environment:
Here's one more presentation type image, again, under full ambient light conditions:
Turning down the room lighting a bit provides really rich saturated colors, the only example, though is on the color bars we started with.
Bottom line, is that the XL1550U does a really nice job on color for a business projector.
Switching to video, I checked out a couple minutes of a couple of movies. Color accuracy - as confirmed in the measurement section, isn't bad for a business projector, but does not hit the ideal 6500K for video (movies). But if you want to take it home to watch a movie, while it's certainly no match for a dedicated home theater projector, the colors aren't bad. This image of James Bond, from Casino Royale, gives you a good indication (it's a little strong on green, which can be adjusted away):
Black levels are of much greater interest to movie watchers than business projector users. Even projectors with poor black levels are normally perfectly acceptable for "business videos" - such as training videos, human resources presentations, etc.
The Mitsubishi XL1500U is not impressive in this regard, in fact, black levels are marginal at best - what you expect from most business 3LCD projectors, and dramatically inferior compared to business DLP projectors. This is reflected in the spec. The XL1500U claims 400:1 contrast, which means poor black levels - blacks come out as medium dark grays. The more expensive XL2550U has improved performance of 600:1, which is a notable improvement, but still far shy of the 2000:1 that is typical of DLP projectors. This is a good reason why the XL1550U doesn't make a great projector for home use. For presentations, black levels are normally a non-factor, as rarely would you project really dark scenes. In a movie however, darks scenes are common, and black levels therefore become important. For our example, here is a night scene of a train, from Casino Royale. the image is intentionally overexposed to reveal detail, but, you can see, that this dark scene is badly "washed out" even though the room was dark:
To put this in perspective, here's that same train scene from a very good $1299 DLP home theater projector:
Bottom Line: You can watch a movie on the XL1550U, but it leaves much to be desired. For business/church/education videos, though, it should be just dandy!