If you can have fun playing a powergamers wet dream this is a well balanced game with a setting that supports everyone being high powered (god-like), which in turns justifies keeping the players challenged. I did some house ruling, but not a 1/10th as much as I did for RIFTS, and unlike RIFTS my Synn. game lasted for 2 years and up to 48th level. Unlike RIFTS, it is also designed/expected for your characters to go to 100th level.
Now was every "character" as equally powerful as any of the others? No, some were definitely more powerful than others, however, they were all cool in their own way, and had some really neat abilities that made them worth playing despite being less powerful. Plus they were close enough in power and usefulness that I never noticed any of the players looking left out, and they sure didn't say they had any problems.
Anyway, we had a ton of fun, I enjoyed GMing it far more than RIFTS, and it is all in one book. You by no means need the second book, even though it has some "nice" stuff in it, so if you do like it (Synn.) you will want the second book.
The only thing that my players complained about, and did so often, was the math and needing calculators. No matter how many times I showed then how to move the decimal place, they still needed calculators. I sat there, saw the damage, moved the decimal place based on the "armor effect", and then added it in my head. Only when they got powerful enough to deal out damage in the millions did I start using paper to "track" my calculations.
The only answer I found is that I was able to add, subtract, multiply, and divide large numbers in my head. Only one of the other 8 came even close to being as good as me, and he could only do it adding and subtracting. Still, I found it far easier than the math in RIFTS, so I'm still baffled, since they say the math in RIFTS as easier.