I have just arrived at a new client site and was handed a pile of MediaWiki wikis, running varied versions from 1.3.5+enotif v1.2, 1.4.0, 1.4.4, and 1.4.7 (I think that's all of them). I'm looking at an upgrade to current (1.9.3, 1.10 if it comes out in timeframe) versions.
I've done some version upgrades before, but never from such old versions. What risks, known gotchas, or issues am I facing here? Should this be expected to work cleanly, do I have a major problem, somewhere in between?
Thanks.