They are a branch of poker.gr as you said Nick which for all I know is a well respected greek poker company. I see advertisments in many top betting/sport sites in Greece and I think they are trustworthy.
Their juice on matchday is about 5.5% which is kinda better from the average of rest european bookies.
Now about arbitrage opportunities, either they have some good-fast trader or I 've lost my old spark
Of cousre some arbitrage opportunities show up but they are mostly low %.
Good betting limits. For example 4500+ Euro on CL games today.
One disadvantage is that they don't offer asian handicaps and their variety in sports is too small (only offering football-basketball-tennis-F1) but they may expand on this in the future.
No live chat, but fast responses from e-mail (max 2-3mins).
I 've made no withdrawal yet, but I will soon.
p.s. Deposits via MB don't qualify for the bonus as helias mentioned. The bonus is only for players from Greece and Cyprus.