SpellChecker performance and usage

[smokey <sm...@gmail.com>]

My question is for anyone who has experience with Lucene's SpellChecker,
especially around its performance characteristics/ramifications.

1. Given the fact that SpellChecker expands a query by adding all the
permutations of potentially misspelled word, how does it perform in general?

2. How are others handling the case where SpellChecker would NOT perform
well if you expand the query adding all the permutations? In other words,
what kind of techniques are people using to get around or alleviate the
performance hit if any?

Any sharing of information or pointers would be appreciated.