In terms of features, NeoOffice (donations accepted) is huge, truly a viable alternative to Microsoft office. It includes all the basic components: Writer, the Word processing component; Calc, for spreadsheets; Impress, the presentation module; draw, for the creation of graphics and diagrams; and Base, the database component. The spreadsheet component has some sophisticated features like Advanced DataPilot technology, Natural language formulas, an Intelligent Sum Button and a comprehensive range of advanced spreadsheet functions.
The next thing to look at, what are the goals of the client? Many clients like personal trainers simply to help them work out, no specific goals but general overall fitness. For these clients, percentages are probably unnecessary as you as the trainer can monitor their intensity and effort by watching. If it is an athlete preparing for their sports, intensities will give you a great guideline to go by and allow you to accurately pick a weight for their work sets that will increase their potential for strength.