Was the DSi really region locked?

I don't believe it is, in an earlier episode of IGN's Daily Fix they said the 3DS will be regioned locked, which is no suprise as the DSi was too. However I can play the US versions of pokemon diamond and pearl on my Europian DSi. Also pokemon black japanese.

The DSi had region locked games but the system itself can still play games from other regions. One example is that you can't play a Japanese Pokémon Black or White on a North American DSi.

It's region-locked only for games which make use of DSi features or its extra processing power. The list of games that have this is larger than needs to be, but here's a hint: Any game with 'TWL' in its product code instead of 'NTR' is region-locked on the DSi.