Better merging would be welcome. But also less aggressive editing/policing.
When I edit openstreetmap I have a better overall experience: the edits may or may not go live immediately, but I don't have the impression that there is someone aggressively vetting/refining my edits while I am still doing them. I feel welcome there.
To make Wikipedia more welcoming, we could do a few things.
We could allow users to save drafts. In this way, people could work for a while at their own pace, and then publish the changes. Currently, saving is the only way to avoid risking losing changes, but it has the very undesired effect of inviting editors/vetters to the page before one is really done.
We could also allow a time window (even 30 minutes) before edits went live after one is done editing (using above Ajax mechanism to track when editor open), experienced editors would not need to swoop in quite so fast on the work of new users, and the whole editing atmosphere would be more relaxed and welcoming.
The fact is that the Wikipedia editor, with its lack of ability to save drafts, poor merging, and swooping editors, feels incredibly outdated and unwelcoming - downright aggressive - to anyone used to WordPress / Google Docs / Blogger / ...
Luca