Are PICO projectors any good for business presentation, light movie watching, general stuff? I've seen some nice units, some at 500 lumens or so, like the fact that they are light, small and very portable. Any good recommendations for business?
They just aren't there yet. They aren't bright enough for proper travel use and they don't have high enough quality for home theater use. About the only serious use they have is as entertainment projectors for kids to use or to take with you on travel to watch movies on the hotel room wall.
They have a lot of potential in upcoming years as brightness increases, but you would be far better served with a traditional projector, especially for business presentation use where lumens matter a great deal. Under $700 there are a number of widescreen projector with more than 3,000 lumens available for use.
If you are truly planning on using ANY inexpensive projector for a business presentation, test it out at home in the same light, at the same size, with the same presentation source. Almost everything is great from a laptop vga/hdmi, but any other sources are questionable and should be tested to make sure they are compatible and to see if the projector has any crash/freezing/remote-control problems. Also, this will allow you to tune your image a bit and see if it's acceptable for work.
For fun and movies; most of the led models above 400lumens are clones of eachother, so go ahead and grab the cheapest version that has the features you'll need. And doublecheck that you can return it if you don't like it. Some online retailers (tigerdirect, newegg) are exchange only and don't allow returns on projectors!
Simple <$250 dedicated black-fabric theater room, build in a day, takedown in an hour.
Easy $25-40 DIY black/dark-grey ambient-light rejecting screen, grab two things from a local store..mix..roll..done.