We have this installed on our forum at consumeractiongroup.co.uk
We are still using vBulletin 3.8 but are planning a move to v.4 - in fact we have already bought the software

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We are a very large forum and depend very heavily on an auto-link system. We couldn't contemplate upgrading our forum without. We were previously using the Geek system and it was very useful but of course won't work with vBulletin v.4.
AutoLinker includes a conversion routine which allowed us to convert all of our links to the new system in just a few seconds. We didn't have to rework everything.
After various teething problems - which have all been resolved, AutoLinker is working brilliantly. We are a free forum run by volunteers and this auto link system saves hours of repetitive explanations and definitions. Also we have configured some of the AutoLink style templates to generate affiliate links whenever someone types a keyword or a keyword string into their post.
We have thousands of these auto links working with no discernible effect on performance.
We will now soon be completing our vB v.4 upgrade. :up:
You can visit us to see it working if you want.