Localization requires fast turnaround of high volumes of material, with rigorous consistency of terminology and style. CAT tools, especially major ones like SDL Trados Studio, make this kind of performance possible. Translators who can transfer translation memories (TM), update them while they translate, and send them back, are crucial to the process.
Even in traditional environments, a CAT tool can increase your production. With a tool pre-translating from a reasonably-stocked translation memory, you could finish twice as much work in the same time. Warning: this depends on how similar the new material is to what is in the TM. My own work data shows an increase of over 50%.
Quality of life: Go from Typing to Translating
Even with a miserable pre-translation (e.g. a new unrelated topic), I have found that a CAT tool can make my work more pleasant. With the segments lined up on the screen, I type only what needs typing. The tool propagates my choices as I work, so when the same segments or terms appear later in the document, I do not re-type or cut-and-paste. Of course, I am building the translation memory as I work, so the next document like this one will have a better pre-translation.
Quality of Work: Consistency
Consistent terminology within a document and throughout a project is especially important in technical translation. This is true of legal and financial work as well as scientific and technical documentation. We are working across cultures, where synonyms and "turns of phrase" burden the readers. CAT tools, such as SDL Trados, allow projects to standardize their glossaries and individual translators to use terms consistently with less effort.
Quality of Work: Review
The most effective way to review is to use a pair of rulers to compare source and target text on printed paper pages. However, some technical documentation does not print well or is intended to be read on-screen anyway (e.g., web pages). The alignment of segments by the CAT tool makes on-screen review easier and more efficient. I still use paper and rulers whenever possible, but I find that translations prepared on the CAT tool have far fewer errors in print, so the final paper check is faster.
Quality and Quantity: Analysis and Management
Translators need to know how to analyze the work, so they can charge fair prices for the different tasks of new translation, total document revision, glossary and TM updating, etc. The major CAT tools will count words, segments and units, analyze text, compare portions of new and pre-translated material, etc. Sharing a common CAT tool as when using SDL Trados, allows the freelancer and the project manager to agree beforehand on how much of the document is fresh translation, how much needs revision. etc.