Could be possibile to create a list of feature available / missing in the sync process for each aspect (calendar, contacts, tasks, notes, documents)?

Essentially the problem is PC Suite. It's always been the worst of the worst PIM managers. No changes were made to the latest version to make the n900 sync seamlessly with Outlook or anything else other than PC Suite, which is limited all by itself. (Nokia is well-known for their lack of good PIM support.) Pesonally, since I am so dependant on PIM, the n900 is for me a borderline device, meaning it certainly has outstanding and amazing innovative qualities, but it also has outstanding shorcomings. That said, I am considering a few workarounds that might save the day, even if they are time consuming and shouldn't really be necesssary at all.

Does PCSuite syncs contacts both ways?

Yes, and the best thing about the n900/Outlook sync. However, there are a few fields that do not sync over to the n900 correctly. all the data comes over, but occasionally I have found field "misses."

Changing / adding info on N900 I'll find it in Outlook?

So far so good, but again, there are limitations, some severe. Contacts are good, it seems, though not absolutely perfect. Calendar: no category sync (they are ignored). Tasks: no. I have a workaround that I am considering, but it is not a fix-all. Notes: If you mean Notes/memos PIM, no, not at all. notes within Calendar, contacts, yes.

Is there any data loss / corruption in this to way sync? (I mean that some fields is silently discarded, etc..

I have not seen any data loss, just some field changes. It's too early to know for sure.

I wish there were a 3rd-party app. One day we may have Pimlical (evolved version of Palm OS Datebk6). Developer states that it will be cross-platform, desktop to handheld, including Linux, but I imagine this is some time off...