What are advantages and disadvantages of turning on "AlwaysUpdatePos" feature in "plus.ini" file? It probably should be used on servers with fast internet connection. I have 3Mb/s download, 0.5Mb/s upload and ping about 55ms (measured on http://jazzjackrabbit.net/fur/si/); should I use this option?

I'm not sure how much I want to keep that feature. The few times that I used it, other players complained that I lagged more than usual. This was on a connect that's 10Mbps down and 2Mbps up, though I live in a America and most clients that join are from Europe. Changes I made in newer updates for JJ2+ should make that command obsolete, but from time to time I still see or hear about "lag clones" (i.e. players that appear frozen in midair and who are unmovable) in a server.

In conclusion, I would recommend not using it considering your connection, but you're welcome to test it out if you want.