More than happy with them both.
When I first got the Smart mini it used to crash a bit but after month or so they pushed out an update and it's very stable. Can't remember last time I had to restart it.
The Smart Mini camera is pretty rubbish but the Mini 4 is better. We will probably never get the latest Android versions but I can live with that.
My previous 'cheap' $200 Vodafone branded Android phone was slow and felt dated very quickly, this one hasn't felt that way.
I'm happier spending $100 every year or so on a good cheap smartphone than $1000 on a top of the range beast that still feels outdated within a couple of years.
There has been a lot of cheap rubbish Android phones about for the last few years, I'm happy some better ones are appearing. Also good to see phones like the Moto G coming out in the next price tier that look great as well.