<p>Is there an Oracle equivalent to MS SQL's full text search service?</p>

<p>If so, has anyone implemented it and had good / bad experiences?</p>

Oracle Text
is the equivalent functionality.
I've had good experiences with it.  Assuming that you are maintaining the text index asynchronously, that tends to be the first source of problems, since it may be a bit between a change being made and the index getting updated, but that's normally quite reasonable during normal operation.