Lucene.Net would be a good choice even if you had the option of full text search.
Lucene.Net expands past what FTS (full text sql) offers. Including boosting terms, fuzzy queries, simple faceted search which can be found in a contrib project on the 2.9.4g branch, etc.
Its opensource so you don't have to wait on someone else's cycle to modify it or have it extended or add features.
There are a couple of posts and even FOSS contrib projects to help circumvent the higher barrier to entry. I'd recommend the content in the list below over starting with Lucene in Action.
The book is a great resource, but the lastest edition is aimed at Lucene 3.0, the java version, which includes newer APIs that have not made it into the .NET version.
Lucene.Net will also pay off as a decent library to add to your overall programming repertoire of skill-sets. Search is pretty much apart of most applications these days.
The Lucene.Net project has gone back into incubation with a newer set of committers and goals One of those goals is to make it more .NET idiomatic and easier to use. However, its definitely going to take time and cycles to reach this point.
In the mean time you can always hit up the mailing lists for help or the irc channel #lucene.net for help.