I think you can refer to their official website.
http://www.selayangstarcity.com.my/v2/about.php

some points i could share with you:

it is a commercial title, 99 years leasehold.
bank loan usually 80% the max.
15km to KL (Tun Razak Road), traffic at Jalan Kuching.
Location wise ok. Apart from the malls, there are some shops nearby, including 99speedmart at walking distance.
The traffic nearby will definitely be improved after they construct those junctions (with u-shape arrows).
too early to say if there would be MRT service nearby but official news have been released that a proposed transportation link from Selayang (or Selayang Baru) connect to MRT 2.
More than 250 shops in the mall according to their latest announcement. all the shops are under rental basis meaning management will have more controls for the lease.

my personal opinion is the value of the unit (Polaris or Vega) will be increased once the mall is opened second half of 2016 especially if they managed to bring in more crowd. The weakness would be the parking lot. only 1 parking lot would be entitled for each unit. hope this helps.