Polonius made a great article discussing the strengths and weaknesses of the imperial guard:
http://www.dakkadakka.com/wiki/en/5th_Edition_Imperial_Guard_Codex_Review_%28Polonius%29
In short, platoons are still viable, especially when merged into one squad for annihilation missions, and split up for objective based games. Guardsmen are cheaper too.
You probably don't need as many as before, and instead should spend points in at least one veteran squad (equipped with either 3x meltas or 3x plasmas, and mounted into a transport). These guys are troops, and kick major ass.
Tactically, they're flexible, cheap, and have a solution to every problem.
MEQs? Plasmas. Armor? Manitcores/Vendetta. Swarms? Valkyries.
Squadrons are dangerous to themselves, as the new rules consider immobilized vehicles as wrecked (but only if they're squadron-ed with another vehicle).
I'm no 'ard boy, so I'd get a second opinion if I were you. What I do know is that people do consider
IG as a competitive/viable army in 5th ed.