Howdy,
I love the idea of Cthulhu and the notion of Cthulhu vs. mechs in the a futuristic setting. I've been working on converting the mechs to Guardian of Order's d20 Mech SRD, which actually converts quite nicely. And in doing so it really gave me insight into what's wrong with Cthulhutech.
Basically, the mechs are an afterthought. They're standardized across the different types of mechs, but there's many different aspects of each mech that aren't handled.
The problem starts with the pictures. This is a full-color hardcover that oddly reduces the pictures of the mech to a few inches in size. Since mechs are pretty complicated things and are an important staple of anime, big colorful pictures are important. Heavy Gear and Jovian Chronicles are a great example of doing mechs right. If you look closely at the pictures, you can see they're actually snapshots of the larger picture in the beginning of the chapter that shows ALL the mechs. So in other words it's recycled art. In addition, there are little tiny representations of humanoids next to each mech picture to give you a sense of scale. Except in some cases the little silhouette is floating ABOVE the mech, half-off of the graphic of the mech, or not there at all. Very sloppy.
The mech descriptions aren't very complete. Some attributes are standard to all mechs but aren't listed prominently, such as the fact they all have artificial intelligence. In some cases there are repeated stats (one of the mechs have life support and a life support pod, which are duplicative effects).
Then there's the fact that the descriptions we do have don't adequately describe the mech. One mech has a "hard point" option to add/remove weapons so that they're easily switched out. How is that a benefit? What does that mean for switching out weapons quickly? How long does it take?
Another mech has hands. It's hard to tell which have hands and which do not from the pictures, but the impression I get is NEG mechs almost unilaterally don't have hands. So what's the advantage of having hands? The book doesn't say. In fact, the book doesn't even tell you where weapons are, so it's not clear if a "hyperedge blade" is sheathed in a mech or carried by it. As I rebuild the mechs using D20 Mecha rules, all these are answered in the rules themselves...but Cthulhutech should have answers too.
What's unforgivable is how the giant monsters that are part of the Cthulhu genre seem to be completely excluded from the actual giant robot part of the game. Cthulhu and his ilk (and he does have GIANT ilk) would be perfect foils for mecha heroes, and yet they're separated out as if they were part of another game -- and none of the giant monsters are in evidence. Instead we have the somewhat lame Migou mecha that look like bugs. Even though the Migou aren't bugs. Honestly I plan to use Starship Troopers bugs as genetically bred monsters for the Migou...cause if you can breed an entire race of alien-halfbreeds (Nazzadi) why not just breed giant monsters in typical anime fashion?
Speaking of weapons, there seems to be an odd preponderance of slowing-type attacks -- there are Grav bombs and some other Migou weapon that slows opponents down. I have to ask: the Migou steal peoples' brains and genetically created the Nazzadi along with those ugly bug mechs...and they couldn't come up with a weapon more powerful than turning you into a slow-mo effect?
A lot of people reference the artwork as being beautiful, but in my opinion it's static and boring. The main inside cover is a bunch of people standing around staring out at something. It's hardly the action shots I expect from a mecha book (again, see GOO's books).
So I'm going to use D20 Mecha (not the D20 Future version) with D20 Call of Cthulhu, mix in Starship Troopers and I think that'll work nicely. If you want a copy of my conversions I'd be happy to send it to you when I'm finished.