Is that good?

Is that good that marblehost has three DCS in different countries?
Do yu trust such companies?

That is neither good nor bad. This is a plus, but comes out compared to the quality rates.

If you wanna get quality which will be good at the any part of the world I may suggest you using glowhost.com.

If there is a principal need in european host - try looking up 7host.com/

I do think when the company provides many DCs in various countries, it makes them more available.

Besides marblehost has provided many free bonuses for their customers - free domain name for life, etc.

Guess it's good to use the closest to your location hosting services.

Would rather recommend american  servers and hosts. Such as cirtexhosting.com for example. This company is among the most attractive for  getting the named service from, IMHO

I like the free hosting bit. Sounds good, but is it reliable ?

I think that if company have multiple DCs in different regions it adds some reliability to them. I know that Grabweb are providing their quality solutions from different DCs and providing stable and quality plans

Think that's good when a company have many DCs in different countries.
Say aspnix, they have two DCs in US and EU and that makes them more available to their web masters all over the IT world. 

If they have good quality then there is no concern

Its good to have hosting company at various locations.

such as different