Instant Expert

Its a great tool for starters, For teams I do not recommend. there are lots of apps that do the same, even google docs is more intelligible when collaborating and working with. But we already have OneNote, Evernote, Word Online, with lots of features way ahead Paper. Pros: Beautiful, Fast, Colaborative Cons: Already Obsolete

A very basic feature like document previews is missing, Any kind of team might loss lots of time downloading files. Anything else is perfect. Pros: Fast, Organized, Free Cons: No document previews

I've been checking out polymail since a year ago, they been a long way, they are costumer involved and have a good team, I think the price is not worth it since there are a lot of competitors offering the same as Spark, Newton, Astro among others. Pros: Beautiful, Multi-platform Cons: Pricey, Offers no features that can justify the price, Other free apps offer the same for nothing or less.