Hi,
I had sometime to test today MemcacheD and Redis.
MemcacheD: I saw no issues or errors anywhere, in a stage site, using all of the features i could. Maybe on a live site, errors could appear, but on a test site i found none. So probably it is working fine.
Redis: Unfortunatelly it doesn't work. A lot of debug errors, Home page has no categories, things seems not to be working right here and there.
The Redis Errors are a lot, most of them:
PHP Warning: Illegal string offset
PHP Warning: array_key_exists() expects parameter 2 to be array, string given
PHP Warning: Illegal string offset 's_slug'
PHP Warning: Invalid argument supplied for foreach()
PHP Notice: Trying to access array offset on value of type bool
Since my port is 0, i tried also 0 from -1, same results.
I wish also someone else could try Redis and let us know. Same Redis is working fine with Wordpress site.