Attack bikes make for a dandy mobile alternative to a Dev squad. Particularly Blood Angels who can get 50 point multimelta bikes.
It's basically a 6-man 3-gun Dev squad thats tougher, able to move (very fast) and shoot for a similar cost.
For C:SM
Consider a comparably set up Dev squad. 6 men with 3 lascannons (similar role as 3 MM bikes) come in at 195
For the same price you can get 3 MM Attack Bikes, exact same price, but more effective penetration (getting into melta range is not hard with a bike) +1 toughness, Twinlinked bolters, which can doubletap and move, and turbo-boost, which is pretty handy for getting into melta range.
Granted, if you're going to go for HBs, then the Dev squad ends up 15 cheaper, but 15 points is a small price to pay for an anti-infantry squad that can move, or even fire and charge.
I would take attack bikes over devastators, but if you want mobile assault, you;re best off going wiht assault squads.
Regular bikes are just too costly for no better than they are.