The only issue I have with my Customizer 104 is that it's enormous, and Unicomp doesn't produce a tenkeyless model. Spacesaver is a little smaller, but about the same size really.
Is it a good choice for your first mechanical keyboard? Absolutely. Amazing tactile feedback, built like a tank, and not too bland looking (provided you get the black one).
It might not be quite as fancy looking as some other "gaming keyboards", but you could probably
dye the keys to pretty it up a bit. That's what I plan on trying with mine. Or you could buy a set of blank keycaps.
So, unless you'd rather spend quite a bit more and go for a tenkeyless Filco with MX Browns or Blues, the Unicomp SpaceSaver is a fine choice.