Judjing by the IG codex I have here, it's not quite as good as you describe. First off, it's more expensive than just 2pts per unit. Second, it only affects the to-hit roll (and only in close combat). Third, it doesn't simply affect everything (except for MCs); you have to choose a specific alien race.
Overall, given the average WS of a Guardsman it might not be too bad, but you'll be specialising your army. The rules state that one should even go so far as representing this specialisation on models by adding various relevant trophies. It also makes it very clear that one should not change the specialisation for each game you play.
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