I just migrated from Outlook to EPIM, because Outlook cannot be reinstalled on my computer due to a very persistive 1935 error (Yes, legal copy!).
1) FUNCTIONALITY: To my surprise, EPIM works even better than Outlook for me, for it offers some functionality, that outlook doesn't offer. For instance: The yearview in calender. That, amongst others, is already a reason NOT to turn back to outlook, even if it would reinstall.
2) PORTABILITY: As EPIM is not as widely used as Outlook, especially not in company/office environments: I really, really like the fact that EPIM offers portability for it's application. That also prevents it for making trouble in my computer, like Outlook did!
I begin to appreciate portable software more and more. Since my computer crashed seriously, I'm very much charmed by the idea a combination of Firefox, OpenOffice, EPIM, WinRAR and WinAMP (all have portable versions) on a USB-stick
3) SIMPLICITY & INTUIVITY: I like the simplicity and intuitivity of EPIM: Actually: manuals, help, nor support were needed until now, and already I have the feeling that I can do everything I want with EPIM (like complex queries, reporting, etc). Outlook has a steeper learning curve. Which by the way is completely understandable, as Outlook is, functionalitywise, more 'oversized' than EPIM. I prefer the simplicity of EPIM, though
Still, there is room for improvement. There are still some bugs in EPIM and there are 'Nice to have's' I'm missing in EPIM. But nonetheless EPIM is a great application, which I will continue using as it already gives me more pleasure to work with, than Outlook did (which by the way, is way more expensive too)