I'm a previous owner of RF G2, G3, G3.5, and now 5.5. I purchased the full G5.5 product at retail on July 10th of 2011. I want Realflight 6, but just missed the free upgrade opportunity that started on August 1st, 2011.
5.5 is a great product, and I don't see a big enough reason just yet without trying a Demo to bother with the upgrade. Maybe when RF 6.5 or 7 Comes out but until then i know i will be sticking to 5.5