Search service was significantly enhanced and streamlined with SharePoint 2013 release. You still need to use PowerShell to truly deploy topology that fits your requirements. Since it's release several Cumulative Updates (CU) have been released. They are being released every couple of months. We hope to see SP 1 soon in early 2014. One CU does stand out and you should take advantage of. This October CU 2013. This is not just fixes but also enhances Search boundaries greatly and provides more flexibility.

Read this article and look for October CU related updates in the Software Boundaries Article for a complete list.

 I have listed down search related updates;

Limit

Before Oct CU Maximum Value

Post Oct 2013 CU Maximum Supported
Value

Crawl databases

5 per Search service application

15 crawl databases per Search service application.

Crawl components

2 per Search service application;1 per server

There is no individual limit for the number of crawl components per Search service application. Instead the limit for the total number of search components per Search service application limits the number of crawl components.

Index components

60 per Search service application; 1 per server

Supported limit per server is 4 index components per server.

Index partitions

20 per Search service application

Supported limit is 25 index partitions per Search service application.

Search components

32 per Search service application

Supported limit is 64 search components per Search service application

Indexed items

10 million per index partition;
100 mill per Search service application

Supported limit of 100 million items per Search service application does not apply. In this case the supported number of index partitions limits the number of indexed items per Search service application. For example, a search architecture with 25 index
 partitions can index 250 million items.

Happy SharePoint Searching!