I own both the ST and the Super. I bought the ST first as a basic flash. For that, it has worked flawlessly. I started doing some portrait work for my DGD's school events. I needed a wireless off camera flash and purchased the Super. I can't compare it to the Pentax or Metz, but both have worked great for me. The DW didn't want anything real fancy so she has the ST in her kit and I carry the super. The only thing I would recommend is to add a diffuser like a Sto-Fen C Omni Bounce.
I haven't used the Metz or Sigma but in terms of wireless, I can say that the Pentax flash works very, very well. The ability to wirelessly trigger from the onboard flash is really a great feature, IMHO.
We just returned from Disney with our new Kx. How many pictures should we expect from batteries? Once we bought batteries 2x in 1 day but it must have been the batteries that day. Could we be doing something wrong that is making us go through them so quickly? thanks
Like the others said, standard alkaline AAs are
definitely not up to the task. It ships with a set of lithiums for a reason.

I would go with the rechargeables, and definitely the low-discharge ones like the Eneloops.
Easily the best deal on the batteries is to buy the
Duracell precharges from Amazon. Apparently it's not consistent, but many/most people are getting what is believed to be rebranded made-in-Japan Eneloops (complete with the signature white at the top). I think some get made-in-China ones but that shouldn't be too bad, either. I recently got my first set and mine were the rebranded Eneloops. One way to tell is that the Eneloops are usually 2000mAh and others are 2100mAh. That's not a guarantee, but it's one indication...
Now, right off the bad, the price is great - it's dropped about $2 in the past month! - $7.79 for a 4-pack. But that's not the
real deal! The
real deal is to use
Amazon's "subscribe and save", where they will automatically ship you new ones at an interval of your choosing - one month, two months, etc, you save 15% on the price (taking it down to $6.62!)
and you get free shipping! And, you can cancel any time - even after your first order. I put in for two months and I am looking forward to my next set already.

For comparison, in terms of "precharged" rechargeable AAs, I have eight Kodak 2100mAh ones, eight 2000mAh Eneloops, and the four Duracells. They are all great, though I think one of the Kodaks started to develop a problem. (Actually, I'm down to six - two were in one of the Disney misting fans which was either stolen or fell off our stroller during our last trip!

) The precharge ones work terrific in our K-x with nice long battery life.
Anyone reading this without a K-x - I would still jump on that deal; those batteries are perfect for flash units, kid's toys, etc.
I am embarrassed to ask so please be nice but I have been reading on the Pentax forums and what does "dial mode to the green button" mean? I read this a few time in threads for new users. The green button that you can assign a function? I don't get it. I don't want to ask on that forum as some people seem put off with questions. thanks
If they're saying "dial mode", they probably mean to turn the Mode dial to the Green square. The Mode dial is the big one on top, with various icons as well as "P", "Av", etc. Green is basically an "auto" mode where you have limited control over settings.
You do, of course, also have a green button, usually used to reset settings - ie, you hold down one button and press Green and it will reset that setting.