New ride - Flat rear - any suggestions?

Hey all,
Picked up a 2011 Raven Stryker a few weeks ago, but I've only been able to get out on it a few times.
So far, I love it (everyone who rides it loves it).

I knew it needed a rear tire in the near future when I bought it, but I wanted to do some tire research first.

Last week, I arrived at my brother's house for a ride, and we noticed the rear was real low on air.
We pumped it up and it seemed to hold, rode and all seemed good. I was leaving the bike there for a week or so, but he called me today to say that the rear was dead.

I've been looking at all the tire warehouses for a good all-weather set (Bridgestone G852's on there right now), but thought I'd drop by here and get some reviews from actual Stryker riders. I stressed all-weather because I am a rain magnet. I also like to ride on the OBX of NC, where the weather is unpredictable and there is no place to hide.

I'm going to keep reading reviews, but now I must act fast if I'm going to order and get 'em mounted before the weekend. Not too worried about the price so much, just looking for a good tire for the Stryker.

Edit: I'm sorta leaning towards the Metzler ME880 (120/70-21 F & 210/40-18 R). $390 for the pair.

Thanks, Steve