Have just returned from a week here with our 2 young children. Originally booked a 2-room apartment which was disappointing and I would agree with a previous reviewer that the standard was more like 2 star. However, we upgraded to a luxury 2-room suite. This was wonderful and well worth the extra money. It had a large private patio and plunge pool; 2 large bedrooms and 2 bathrooms and was of 4-star standard.
Public pool area was great - plenty of space and plenty of sun-beds whatever time of day you turned up (unlike the experience of a previous reviewer) - although we did start our holiday on 29th August so probably past the really busy period.
A good play park for children and pleasant gardens.
Mostly Scandinavians staying there and a few Brits, Germans, Eastern Europeans etc.
The nearest walkable beach was large and sandy but quite windy with big waves when we were there. Much nicer sheltered sandy coves could be found at Agioi Apostoli (about 4-5 mins by bus towards Chania) which felt relatively unspoilt with 1 or 2 tavernas but still had loos and showers and also sunbeds for hire.
Don't miss the old town and harbour of Chania if you go - fabulous market, shops, restaurants, scenery and architecture.

Myself and my Fiancee have just returned from a couple of weeks in Crete, one of which was spent at the Sirios, which turned out to exceed our expectations.
For what we paid, we were expecting something cheap and cheerful, with the usual crispy bread and rubbery cheese for breakfast, sullen, underpaid staff and an overpriced Bar.
What we got was a very friendly hotel, that served excellent food, had a well equiped pool area, and very clean rooms.
It's also set back (approx 500m) from the main road, which means it's really peaceful (alot of the hotels in this area are built along the Rd - A road that's busy and so consequently noisey, 24hrs a day)
Very popular with Scandanavians and Greeks, this is a great hotel for families.
I think the proof of a good hotel is weather you would reccommend it to your friends - but as I dont have any of those, I'll reccommend it to you.

The Sirios is perfect for families seeking a holiday around the pool but not so good for couples and single travellers. The rooms are to a very good standard, the meals are either very good or average (diifers from day to day) and I found the staff to be very pleasant.
Kato Daratso is a quite resort and so a taxi ride to either Chania or Agia Marina is the only way to find any decent bars (very few people use the hotel bar at night)
I would return again but maybe not during the scandinavian childrens holiday.

Not sure how the hotel got its 4 star rating - definately not for those seeking a peaceful holiday in a quiet setting. We felt it was 2/3 star at the most and the facilities were not great. Quite crowded by the pool area and not enough beds we found.
Food - bland - but i suppose to be expected in an all inclusive complex of this size - shame really as Chania is a very pretty area in Crete - and we did venture out to find some authentic Greek places to eat in the evenings.
Overall poor - would not go back - but it probably will suit a family on a budget.
Even the staff looked fed up - and that says it all!