First from reading and re-reading the description of the app, there is no mention of cut, copy and paste for Quicksheet, to me the absence of cut, copy and paste in a spreadsheet is a show stopper. Per the description, Quickword does have cut, copy & paste, but the first user review claims that Quickword omits auto-correct, auto period/capitalization and/or a spell-checker - again, if this is correct, this is a show stopper for a modern day text editor. Another concern, Quickoffice does not appear to have a Powerpoint viewer/editor, from what little information that is available for Documents To Go, DTG appears to have at minimum a PPT viewer. If you happen to use iWork 09, Quickoffice mobile suite is currently not file compatible with Pages or Numbers.
In conclusion, there are just too many questions to be answered before purchasing Quickoffice, especially considering that DataVis and possibly Microsoft are waiting in the wings with office suite applications for the iPhone. At this point I am going to wait to read the blog reviews and user reviews.
[UPDATED - Sun 4/19] - There are now several user reviews (12 reviews... only 2 are 4 stars or above) on the app store for Quickoffice 1.1.0, a new issue is discussed... Quickword does not provide a process to email documents, nor can you edit documents (.doc or .xls) that are attached to email on your iPhone. You have to move files on and off your iPhone via wifi from you desktop or leveraging Quickoffice's link with MobileMe. Still no mention of Quicksheet... does it have cut, copy & paste?
UPDATE - Mon 4/20] - Value proposition... I am OK with spending 20 dollars on an iPhone application, if the application fills a need and is a "go to" app on my iPhone, to me, $20 is a bargain. A "go to" mobile application will have higher usage than its desktop counterpart. That being said, for Quickoffice Mobile Suite, issues aside, it is hard to justify the $20 if you purchased Quickoffice Mobile Pro (now Quicksheets) for $9.99 a month ago. The suite product is essentially the same as Quicksheets with the addition of Quickword. Essentially you are paying $20 for Quickword. Buyer beware.