Apparently the A90 is EOL'd (not being made anymore).
I ordered mine about a week ago, last Friday they (Dell Germany) were selling the A90 with insane rebates (less than the price of the Mini 9--or so I heard, if I had heard about that earlier I'd had gotten another one!), and when I looked two days later the model had disappeared from the Dell shop completely.
When I complained about some minor problems (scratches, stuck key) with my A90 I got the answer that they could just refund me, but I couldn't get a replacement since this model wouldn't be made anymore (not that I wanted to give my A90 away anyway).
It's still listed in the US store, so maybe it's just the German store, maybe not, so keep that in mind if you're planning to get the Vostro.