"hard" pads to me are the original everglide pads (plastic) or the once popular icemats (glass) or similar (steel etc.).
i was going by what i saw in the galleries of the latest events. most people seem to use either the black qck heavy or another qck version with a sponsor logo on it. even the pads by razer i recognized i would put under the "cloth" label.
I bought 2 of them about nine months ago (imported, so +1 spare), used one of them but decided after i visited my 2nd event with it that i prefer my qck. I find my hand sticks, or bumps along the puretrak talent more than the qck, this "issue" is amplified if your room/area of play gets cold/damp (high humidity) and could occur if you left the window open during a cold evening for example (the event i speak of was in a temporary structure, very cold after everyone went to sleep), or if you have cold hands.
i.e. I find that the puretrak talent is at times just awful to play on with the way i play, and that my older steelseries qck doesn't suffer as much from that problem, which i guess is due to the material they have used for the surface. Since i plan on attending more events this year and next, it's not really a mousepad for me.
That said, there's nothing specifically wrong with the performance of the pad with regards to tracking, when everything was "warm" it was no different to any other pad i've used, it's pretty durable and it hasn't lost any of the surface. So if you've already bought one - you won't really be dissapointed.
I think mx518 can handle all kinds of mousepads - it's no laser after all - but please correct me in case I got that wrong, you should make your mind up if you want either a cloth- or hardpad - maybe try the difference in some shop in your area
from what i'm hearing those are relatively popular:
allsop raindrop
qck heavy
qck
goliathus speed
and the few that were mentioned earlier in this thread
I received the mousepad today, and I ordered it over a month ago. Anyway, the pad is Huge, smooth, ect. But imo my old icemat beats the crap out of this pad when it comes to tracking.