I'm actually getting SZ50EP's put on at a Firestone place this weekend. It actually started two weekends ago. I looked at them Saturday and decided Sunday to get them. They had just put the last set on a Camaro, so they said they'd order some during the week so I could have them last weekend. There was some mixup and they didn't get ordered, so now I get free lifetime alignments too since I have to wait until this weekend. I later found out that I just happened to be dealing with the store manager the whole time, and the other girl working said he was talking about the Sy for hours after I left. =)
Buying tires there, I got free "mounting", even though they still charge me for the balancing labor and weights and everything. With shipping from Tirerack, it was about $620 for the tires. With the $80 road hazard warranty, I'm walking out of the Firestone place paying $800. It's basically coming out to exactly the same price for me, but I won't have to deal with internet crap if I have a problem, which is worth it to me.
They quoted me $192.99 each for the tires. They were having a "Buy 3, get the 4th" sale, but high performance tires were excluded. So he just dropped $25 off each tire. $168 compared to the $155 that Tirerack is charging...
A friend of mine said he heard some bad things about the SZ50EP's last spring when he was looking for new tires. Something about the second "EP" layer being crappy, so you get really good tires that wear down to really crappy tires. However, the only bad things I could find about tires was their performance in snow (that's what happens with summer tires) and their cost, which still isn't that bad.
http://syty.net/phpBB/viewtopic.php?topic=9922&forum=3
I was also considering the RE730's, but I read quite a few reports that they got quite noisy... I think 892's story in that thread is what finally convinced me.