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Many users may never miss these features. Yet for others, the superficial improvements to the interface may seem too little compensation for all the missing functionality, especially since the change is not accompanied by any lessening of system requirements.
In fact, the reverse is true -- Symphony requires a substantially better computer than OpenOffice.org. Where OpenOffice.org on GNU/Linux requires about 200 megabytes of hard drive space and 128 of RAM, Symphony needs 750 megabytes on the hard drive, and 512 of RAM. Some of Symphony's extra requirements seem due to the clipart and Presentations backgrounds that it includes, as well as the need to install Eclipse and Java with it (in OpenOffice.org, by contrast, you have the option of not using Java, at the cost of losing a couple of little-used features).
All the same, in many ways, Symphony seems too little, requiring too much. Even with the changes that are likely between the current beta and the official release, it is hard to imagine Symphony improving enough to justify the added system requirements -- especially when you consider that the specs listed are a minimum, and should be doubled for both applications if you want optimal performance. Yet, even so, Symphony performs poorly when compared with OpenOffice.org, which nobody has ever accused of being a speedy program itself.
If you are a Lotus Notes user who wants integrated office applications, then Symphony is worth trying. Otherwise, the most you can hope is that some of Symphony's interface improvements might eventually find their way into OpenOffice.org, and lose the weaknesses and arbitrary changes along the way.
Given that OpenOffice.org is more fully-featured, makes few hardware demands and is under a free license, replacing it with Symphony seems pointless.