Mesembs (we call them 'ice plants' for some unknown reason) do very well down here in NZ and can make stunning groundcovers but I have found they have the nasty habit of harbouring snails and slugs in winter and also promoting collar rot around some of the more fussy or wimpy aloes etc. But you guys probably know that and I suppose it wouldn't be a problem in drier winter areas. Those with winter rain should be aware of these issues, though.
And when they get caught by a rogue frost and go sludgy, it's on an epic scale
Not everyone loves 5m square of electric purple or pineapple yellow blooms but if you can handle the jandal, they're very *ahem* impactful.