The X1 uses the second generation ZF 6HP which is much improved over the first for gear changes. This second generation can skip up to 4 gears and can actually do some gear changes faster than the 8 speed. The 8 speed can do all gear changes in right about 100ms. The 2nd gen 6HP can do some in 80ms and worst cast is 200ms. I spent probably 10 hours doing some very in depth research on these transmissions (though I don't want to claim I know it all and maybe someones report was inaccurate) but the 6HP is a very good transmission and has about half the parts and will change gears less making it more likely to have fewer problems.
Here's an article I quckly googled about skipping gears in the 6HP http://wardsauto.com/news-amp-analys...p-transmission
Somewhere on my home computer I have pdf docs that go over various shift times in the 6HP, also found via google but I don't have the link handy.