I am not using MS Office for iPad, too pricey, but I did need an Office compatible suite and luckily stumbled upon a temporary free deal for OfficeSuite Pro, which is meeting most of my needs (compatibility, speed, ease of use, working with miscellaneous cloud accounts).
Other apps I tried but didn't like:
iWorks - beautiful design but modules are huge, very poor Office compatibility, Office docs comversions are slow and lossy, iCloud apps on PC are very slow, Numbers is limited a bit vs Excel. Good if you don't have to collaborate with MS Office users, don't use MS Office file types often, and aren't concerned with storage size.
CloudOn - probably the best direct compatibility with Office files, even supports macros, but slow start up and needs internet connection to do anything
QuickOffice - only good for Google Docs
Olive office - buggy