Hard shifts.
I just bought this car today. For $1500 it seemed like a deal.
The sunroof is bound up. The brakes are noisy. It has not been driven much lately.
I saw one comment that suggested that hard shifts were typical, but I wonder?
Yup, it seems like you got a good deal. I can't find a single one here in California for under about $3000 USD. And the $3000 ones need work.
BTW, diesels in general shift sort of hard under hard acceleration. They don't tend to generate a lot of vacuum which controls the shifting. Check to make sure that all vacuum hoses are connected properly under the car.
Also there is a 'vacuum modulator' under the car next to the transmission pan (this also controls the firmness of shifting). I wouldn't suggest you mess with this unless you are confident in your mechanical skills. You will never be able to make it shift completely smooth, you can only adjust shift points (when it shifts) and slightly how hard it shifts.
ALSO, if you haven't already done so, have your transmission fluid, filter and gasket replaced. Don't do a flush because a clogged filter can also cause hard shifting and eventually lead to a bad transmission. So yeah it was common, but you can dial it in a little bit better. Good luck.