I love Boots!
But it does depend on the store itself, I find.
The local one to me is small & fairly rubbish - run out of stuff quickly and have a v limited range.
The big one in town is BRILLIANT. And I can always find something to spend points on - and they do sell high end cosmetics, so I can properly treat myself rather than buying baby wipes with them.
They also have a UR Beautiful salon, where you can collect and spend points, so I have no complaints at all.
Their online presence is pretty poor though, compared to others. Slow delivery dates and rubbish 6 hour time slots (last time I tried). In fairness to them, I did complain via their feedback bit on the website, and they came back asking for more details...but I got a bit bored and didn't bother replying 
One place that really cheesed me off was Sainsburys. Last time we used Nectar points, it paid for somthing in full (flights or Eurostar IIRC)
This time, we wanted to buy a washing machine from them - you can only use £50 in one transaction! Unless you are buying in store. And we had £350 to spend. (It sounds a lot, but we've been collecting for about 5 years and God knows how many £££££ we've spent on the way)
So, Plan B was to buy the big Christmas shop and a few presents, to use them all up.
3 hours later and having put it all through the till, DH hands over his card. Error message: Points not redeemable. I hand over my card - 'sorry, we can only scan one card per visit, you'll have to call Nectar to sort it out.'
I went into meltdown.
DH calmly states we'll just unload everything and put it all back through the till.
Funnily enough, the manager went off to find someone who knew what to do. Reader, we spent all our points. And a bit more 
Despite all this, I still wouldn't stop shopping there. Muppet.