Developer: Mariner Software, Inc.
Price: $4.99 Download on the App Store
Mariner Software's Mariner Calc is the second app that I've looked at on the App Store's productivity shelf capable of viewing and editing Microsoft Excel spreadsheet (.xls) files. The first was Quickoffice's MobileFile's Pro, which I liked very much.
Both apps handle Excel files on the iPhone in nearly identical ways. They feature the ability to create and view .xls files; cut, copy and paste; support multiple worksheets; set typeface and font styles; insert columns and rows — in short, everything you might expect them to do.
Mariner Software says Mariner Calc supports 145 functions and Quickoffice says its app supports 125 functions. I have no idea if either claims are true. Both seem equally capable to me. I wouldn't use either to create spreadsheets on my iPhone. There's just not enough visual real estate to do that, so I'm mainly interested in viewing files and making small tweaks. I suspect the same is true for you.
There are differences between these two apps in their Excel functionality, but only two that I would call significant. Mariner Calc features the ability to split and freeze panes and edit and view Excel 97 files and up. MobileFiles Pro, on the other hand, does not feature split/freeze and can only view and edit Excel 2003 and only view (not edit) Excel 2007 files.
The UI for both apps differ as well but I found both equally easy to use. Mariner Calc relies on slot-machine wheels for some tasks where MobileFiles Pro uses a menu list of pop-up icons.
Both are capable of wirelessly shuttling files back and forth between the iPhone and the desktop.
MobileFiles Pro, in comparison, has features Mariner Calc lacks. The most significant in MobileFiles Pro is able to email files from within the app and transfer files to your iDisk account where you can create folders and manage your files. It also has a superior interface that makes the job of transferring files to and from your desktop dead simple.
MobileFiles Pro also has a robust file viewer for viewing a wide variety of files (.jpg, .ppt, .pdf and other common formats).
So which one would I recommend? Both are similarly priced, so cost is not an issue. For now, I'll stick with MobileFiles Pro. However, if you need to view and edit .xls files other than Excel 2003, then Mariner Calc is the way to go.