Overall I would give Tas a thumbs up.
Tas is definitely one of the more stylish, design derived builders in Toronto. Their buildings/presentations stand out and that's what this city needs more of in my opinion. Dia, Giraffe and M5V are all very good looking projects in my opinion. Dia, especially, stands out along the very bland glass and steel corridor that is Yonge between the 401 and Finch. I'm sure Giraffe and M5V will do the same. They are also a very environmentally friendly builder. Tas was named green builder of the year, and there is literally an entire table of awards in the Giraffe presentation centre. Both M5V and Giraffe have been registered with LEED and will be LEED cerfitied upon completion.
That negative comment in the link you posted seems to be quite far fetched. It sounds like that guy's entire unit collapsed on top of him and all tas and tarion did was laugh at him. Unless you're buying some ultra-luxury, ultra-expensive new condo or home, you should expect problems. It's just the nature of the new home/condo environment. Delays are also very common as well, very few highrises are completed on time. Giraffe will almost certainly be delayed, mainly due to their OMB troubles.
My main criticism of Tas is that they are somewhat of a controversial developer. Giraffe is involved in one of the biggest OMB battles since the Queen West Triangle and Dia wasn't exactly approved right away either. It makes one wonder that if they were more conservative in their design and locations, they would save themselves and their customers a few headaches. But that's the kind of company they seem to be, and there's nothing wrong with that in my opinion. They're almost like the Alfa Romeo of condo companies while Concord Cityplace and many, many others are the Toyota. Stylish with soul and headaches vs. bland and boring but reliable.
Bottom line in my opinion is if you want a typical, run of the mill glass and steel box, don't buy from Tas.