r888s are fine in all situations apart from when there is standing water... even then, just slow down when it's very wet and you'll be fine. They won't last long though and it's a total waste of money, especially now that the new r888s are out and much more expensive.
Zentums are okay and maybe better than the average tyre of the same price... I'm not entirely convinced of that yet. I have a set on my WRX and don't feel particularly confident in them, especially in the wet... I used the same set on my Legacy for a trip to Hamilton and they felt pretty good... but the limits of the Legacy are very low compared to a 90s WRX and I still didn't like them in the wet in fast corners.
Yes people, well Sam, has used them for autox and street sprints with some good results, but that just means that Sam has adapted well to the tyre and he would likely do as well with any old tyre that he was accustomed to.