I think lot of utilities and services come out of the box from the Open Source for different purposes (IDEs / Application Platforms / Testing Tools etc..). These things if we were to develop takes lot of time and effort. For eg. Apache Software / erstwhile Sun's dev.java.com are very good sources around which lots of products(Even Commercial ones) developed. One very good example is petals. You can see lot of products that are built around NetBeans / eclipse, taking them as base.
I feel that and my experience in Open Source Product Development also says that its always good to search (if one such library is not available or known also) prior to writing one's own code for libraries. Precautions that must be taken are
1. to look at the Licensing Model around which the component is available.
2. Support for that product . If commercial support is available (which would be fractional when compared to proprietary code) its better to go for it since you will anyway get support.
3. Mailing threads / Discussion board activity on daily basis -- since in dev. turn around time is very important.
4. community response time.
5. Documentation Quality that is available -- This plays a vital role too.
6. Access provision to the source code -- So that depending upon the licensing some of the code might be reused if required.
If we choose the library / utility based on the above criteria it always lessens the amount of work.
