r33cruiser is right about the cost, the EMU was not cheap
plus, as he said not many tuners like to tune it (which is a valid reason not to get it).
For me, I find it awesome because I am technical person and love to play with it. I record drives almost daily on my laptop via USB 2, analyse the graphs it records and adjust the tune each night. I find it easy and fun.
My last tune on the dyno (by my mechanic) yielded 323rwhp @12-14psi (sorry I am turbo)
With the EMU I can maintain a pretty consistent desired AFR and I can modify ignition timing.
If I was manual I probably would have tried to source a PowerFC - I've heard so much positive info about them, however they are hard to find these days.
The SAFC is cheap, and looks good, but doesn't allow tuning of ignition timing (which is where the best gains can be found). I have a friend with one on a Honda and he is happy with it (so simple we wired it ourselves)
After getting my EMU, the NisTune chip came out which my mechanic has been promoting since. It may be another option for you.
I wouldn't say don't get the EMU, but I would agree it is not the cheapest option and requires some patience to get setup and get results.
I also agree with the above posts that money would be better spent on other mods first. I only needed the EMU because I have heaps more airflow since upgarding the turbo.