IMHO, Aurora FM is one of the very good sounding FM Software synthesizer that you could find in the market. I have been using it in many of my projects for the last 2 years, it has never disappointed me. Even in its raw form, I find the sounds from this synth to sit relaly well in most of my mixes. With a little bit of thrid party FX (Delay and Reverb to be specific), the sounds can be further improved. On my 3 years old laptop, this plugin does not eat up much resources (mostly in signle digits) even with multiple instances running.
Ryan (the developer behind this wonderful plugin) has been simply amazing with his constant mailers (no spamming) and important updates to the VST. He is also a very friendly developer who listens to the customer's suggestions on imporving the plugin.
I highly recommend this VST for anyones who is looking to add some fine FM goodness into their prodcution.