So, I've read that getting a visa at the border in Tanzania is not such a big deal...but how about in the case of coming from Uganda? Thank you!

Hi,
It's not a big deal - not even from Uganda.
Regards
Hans Kristoffersen
Editor
Mwanza Guide 'online'

For posterity... I ended up getting my visa in advance, which was much cheaper than if I had bought it at the border. I ended up crossing with another guy and he had no trouble to get his visa. He changed some money with a very friendly guy outside the border post too, no hassle. The guys in the post were so nice. They asked how long I was staying and when I told them they were like, oh, is that all? You should stay longer! Tanzania was really great.

How much was the visa on the border? I'm currently in Tz on a single-entry visa and will soon be travelling up to Uganda and back again.
#3, if you're still within the time-frame of your original single entry visa for TZ, you won't need a new one to re-enter from Uganda, it will still be valid. If it has expired by the time you come back, a new visa will cost you either $50 or $100, depending on your nationality. For most nationalities it's $50.