I don't really agree that Voyager suddenly improves half way through season 6. I feel season 6 started off with three extremely strong episodes in "Survival Instinct", "Barge of the Dead" and "Tinker, Tenor, Doctor, Spy". The whole season is filled with some very good episodes and the occassional stinker. Its a pretty consistent mixture for me. I certainly don't think "Collective" and "The Voyager Conspiracy" are more interesting or of higher quality than "One Small Step" or the 3 episodes I mentioned before.
It seems you were getting fed up with Voyager in season 5 which is understandable if you're getting fed up due to the samey-ness of a new adventure every week format, but not really judging by the quality of episodes, I think season 6 is only slightly better and season 5 has some huge standouts like "Once Upon a Time", "Timeless", "Counterpoint", "Latent Image", "Dark Frontier" and "Someone to Watch Over Me".