A lot will depend, as with any printer, how the source files are prepared and what quality they're prepared at. I also must point out that, unlike most print-on-demand services, Lulu will print whatever you want and isn't terribly restrictive about content. Most POD services are horribly restrictive, so if you have anything "controversial" or adult-oriented, or anything like that...forget about using anything else, at least once they find out what you're printing.
Lulu's quality is comparable to pretty much any other print-on-demand service. I have heard of some people having quality issues with them, but I actually have never had any issues. When I was doing the convention circuit for a couple of years, I constantly had Lulu-produced books with me, and they were never anything but excellent. They are my #1 choice for printing, though the primary reason why I esteem them is because they respect me as an adult and don't put a bunch of ridiculous, restrictive terms on me and my work. Yes, they are a little more expensive than a number of other services...but at the same time, considering the works I printed, I more than made that back through my sales at conventions.
It's incredibly easy, all things considered, to print with Lulu. If anyone is having quality issues, I'd be more tempted to believe it was a problem with what they submitted and used as sources for their printing than to believe it was Lulu's failings. Lulu have been really upstanding and reliable in all the many, many years I've used them, which is basically since they opened. Take that as you will.
