You won't be able to threaten any vehicles on your first turn except with the reaper which is nothing to write home about.
So you won't be able to take out any threats to your army that are armoured. A good opponent will either take out your blasterborn on his first turn (or first two turns if he goes first) or force you to deploy them so conservatively hidden out sight where it will take them longer to get to the action.
You really need some ranged AT, blasters is transports won't cut it against a Mechanised Guard army, AV13 Blood Angel spam, or Tau Mech (the suits can stay safe by jump shout jumping behind their transports, and therefore staying out of sight of your splinter fire).
Basically any form of mechanised/ alpha strike army will give you problems, because your lacking ranged AT on the board turn 1. At least that's how I see it.
I would try and find a way to get some lances in there.
Hope that helps.