I have about the lowest tolerance for foot pain of anyone I know. Therefore, I live in flip flops for approximately 8 months of the year (and p.s. I do not live in a temperate climate by any means) and UGGs for as much of the rest of the year as possible.
Unfortunately for me, I haven't chosen a profession that has accepted flip flops or UGGs as footwear choices for the workplace...yet. Ever. :( So I am always on the look out for comfort enhancing measures and comfortable shoes. My newest shoe love is Sofft brand heels - they are by far the most cushioned, balanced shoes I've had. The heel feels incredibly sturdy, and the footbed is one of the only ones that doesn't cause me ball of foot pain within a new hours.
My newest comfort-enhancing measure is heel liners. I bought a pair of incredibly cheap but incredibly cute flats not too long ago and wore them for a few hours to come home to shredded, bloody heels. (Sorry) The results of those 2 hours plagued me for a few weeks as I desperately tried to find shoes that didn't rub on those places on my heels. It sucked. Now that the heels are healed (lol)...I would like to be able to wear the flats again.
Dr. Scholl's For Her Heel Liners -(here - I paid $6.99 CDN at Superstore)
These are essentially thin curved pieces of soft plastic that stick in the backs of the shoe. They are supposed to both prevent rubbing/pain on the heels and to help heels not slip out of shoes.
First of all, they stick on well and don't seem to be going anywhere. They're fairly thin and unless a shoe is already tight, they don't change the fit a lot...although they seem to be making my cheap flats widen out a little bit when they are on the foot.
In terms of preventing rubbing, they're great. They have totally transformed the back of my cheap flats - they had rough edges that rubbed before and now with the liners in, the backs are smooth and soft and comfortable.
In terms of preventing heel slip...they're ok. I always have the issue that heels that fit with bare feet slip at the backs when I wear nylons. So I put these in a pair of high heels that slip for interview week because not only does slipping look sloppy but I find it causes foot pain and tiredness because I tend to grab with my toes in order to combat the slipping. They do an okay job of preventing slipping - more because they add grip but I still found that as the day went on, I got a bit of slipping in my smaller foot.
Overall, I'd give these a 3 star (***) or merino rating. They're good, they're cheap and if you buy shoes that cut your feet, they will stop that, for cheaper than it costs to actually buy decently made shoes. They may also help the nylon slipping problem for you, but I'm not guaranteeing it.