I wrote on another blog I bought an iPad to help when I'm away from my computer. I never liked, wanted or needed a laptop. When I'm out of the office I focus on other things, and if I work on Web stuff, I work from print copies to review and edit. That's the way I work, a copy of the pages, a pad of paper and a pencil, and ok, a big erasure. Traditional but it works.
Anyway, I've been testing the various PDF readers available for the iPad, and while I only tested a handful - I'll leave it to the testing bloggers and Websites for the complete reviews, I found two which I find good, and one very useful namely because it handles big files, upwards of 300+ Mbytes and maps, especially USGS 7.5 minute topographic maps. But even that said, there are caveats to the PDF readers on the iPad.
For one, they're not full fledge versions of the PDF applications, like Acrobat, but then even Apple's iWorks suite, Pages, Keynote and Numbers are trimmed versions of the Mac versions. This reduces the size of files you can work with and the tools, functions and features available to the user. But still they're quite useful with the sheer number of PDF documents on-line.
For another one, they have issues, or more so problems with newer publications of PDF's where the photos, images, maps, graphs, etc, are sliced. They simply display as white space. But there is a work around, explained here. It's simply a matter of opening and resaving the PDF which compsites them back into single file in the PDF, after which the PDF readers are fine rendering the document.
But the point here is that the iPad is cool for carrying these along instead of the paper copies. Ok, so do other readers, lots of books. But the iPad has the rest of the tools, which those readers don't have or can do. I use it to research Websites, minus the flash-based ones and others with display issues. I can displapy portfolios of my work. And among the other tools, it has Google maps with a location (built-in GPS) finder.
This last feature is what I tell people now. Now I can prove I'm lost, "See, it's right here on the map. I'm lost right here." How cool is that to know where you're lost? I haven't taken it to Mt. Rainier NP yet, but it's on the plan, and I'll keep you posted all the neat place I got lost.