Would I suggest using them as an 8051 source?

Since I've never heard of them before you mentioned them on this forum, I'd have to say no, probably not.

My question is why do you want to consider using their product? The most cursory glance at their web site reveals that they don't fabricate their own parts. Who does? Do you want to use them to save money? Can you save just as much by going to the manufacturer? Do they really sell enough parts to get enough volume discount to beat the manufacturer's normal pricing? If they can beat the manufacturer's normal pricing, how do they do it? Are they selling parts from the 1-sigma bin? What kind of project do you want to use them in? Is it something you're building one copy of? Or will you build 1000s. Can their parts be second sourced, or will you be married to them once you use their part? What does their part do that Atmel's or Philips' or TI's or AD's won't do?

Would I suggest using them as an 8051 source? Maybe if they pay me enough. Or maybe not.