Currently the extension is under observation because instances of heavy server load/unstability has been reported. It is not yet clear if THIS extension has anything to do with. So it's only under suspicion at this point until further data has been collected. But for now it is advised to be careful with the application of the extension for mission critical, high-load environments.
It's still uncertain how performance is under heavy load conditions and when MANY pages are indexed. Currently benchmarks have been done only up to 2000 pages indexed/approx. 400.000 relation records. It is likely that some parts have to be optimized for such scenarios.