i used to use ratlings as an annoyance unit, but i found that during tournament play mostly, they were always starting in reserves as they were an elite unit... (and i couldn't land a mission with 'infiltrate' if my life depended on it!)
while the "go to ground" rule does help them with cover saves, i find the T2 is a *huge* weakness! most times i find i'm rolling so many cover saves that it doesn't matter - i always fail just enough to lose the unit.
i also HATE! the models
ugliest things ever... i converted up a couple plastic guardsmen to mix in with some metal snipers like the mad larkin model!
now though, i've gone back to the special weapon squad snipers. a few ablative wounds, the ability to benifit from doctrines and a better toughness is much more desirable!
besides, i only include them to make my opponent think twice about where he/she will deploy that big death gribbly
even in games were those 3 snipers haven't even hit a damn thing! (yes that's right, tripple 1's two turns in a row and then they died...) the fact that my opponent decided to deploy their big nasty somewhere else just to avoid being in the sniper's LOS was more than worth it
cheers!