The only things I don't like about my Super Tigre engines (.40, .45, .90 and G2300) are:
Needle valves. I don't mind the needle being in the traditional position, but the design makes making extensions a pain. Thunder Tiger has the right idea which is now being copied by OS. [&:]
Mufflers. Who designed those things? Obviously not a real Italian. Ugly ugly ugly...[:'(]
Weight. The whole line is on the heavy side.

I love the warranty (3 YEARS!), performance and price. All mine run really well, are easy to tune and have been trouble free.