When considering a new ASIC design, carefully consider the role Analog will play in its deployment. To minimize risk, choose your ASIC development partner carefully.Most of the time, non-critical Mixed-signal ASIC design skills (meaning an ability to cut and paste functional blocks from a cell library) will be sufficient.
For those applications when the Analog performance is critical, you need to minimize your risk. Custom Analog Design is the only way to assure your product's peak performance. Always seek out an Analog ASIC partner with the right Analog design skills and experience to match the application. To help you understand the benefits of a full custom apporach, go to JVD, Inc. : Whitepapers : ASIC Design, Manufacture and Test