This is true. You just need to keep this all in mind while you're living there. It will be more developed over the next 5 years, but even after the 2015 Pam Am Games have come and gone the development will still not be complete. You'll be looking at upwards of a decade before this area truly comes together.
If you can live with the lack of retail and amenities for a few years and be excited about the progress while it's slowly taking place outside your window then this may be a good decision for you. You need to take a long term approach. Even people living along large stretches of King West are still looking forward to future retail and amenities. You will be close to the Distillery, St. Lawrence Market, and it's a short street car ride to Yonge Street. But when you walk down the street and there isn't a grocery store, dry cleaner, or ATM for a number of blocks that could get rather old and tiresome.
However, that's no different than the suburbs where there may be nothing for miles and a car is a necessity. Actually, Corktown is not anywhere comparable to the suburbs. It definitely is very urban and has an interesting vibe. I guess what I'm trying to get at is that whether you live in an established area, an up and coming neighbourhood, or a suburb it all depends on your lifestyle and what you want to get out of the neighbourhood you live in.
I was looking for a place in St. Lawrence Market and "veered off" into Corktown because I was interested in the development of this area. I seriously considered it provided that I'd have an exceptional suite for the same price as the smaller suite I eventually purchased in St. Lawrence Market. I liked that it was only an 8 minute street car ride to Yonge, there are some charming local small businesses, and it would be neat to be part of the great development from the very beginning. But, ultimately, I know myself. I need to have it all at my front door. I'd rather walk down the street with my cafes, bars, restaurants, grocery store, cleaners, and a subway stop within walking distance. I know myself just as someone who loves a big house in the suburbs with a nice lawn and a backyard patio knows him or herself.
It's a lifestyle choice you're making. But one that could be very good for you over the course of time.