Which version is this elvisboy, is it the OS version?

It's the sr system, I assume you are using a tripod, if so it is recommended you turn off sr.

When using a DSLR there are only two rules.
1. get a manual lens and learn how to use it by...
2. RTFM
over and over and over trying out everything it offers and settling on what you like best.

I witnessed something similar on the M4 at Port Talbot years ago. The traffic was slowing to a stop and alongside me in the inside lane a couple are having a right ding dong in their Escort, I tooted my horn because I could see that the traffic had stopped but he reacted too late and smoked his tyres as he stood on the brakes.
I remember vividly the Volvo rear bumper compressing all the way back to the body and then simply returning to its normal position after taking the impact of the Escort, not a mark on the Volvo.
The front of the Escort was by now a whole foot shorter, its headlights had shattered all over the road, its radiator was gushing water and coolant. And boy did she rip into him then, I didn't think it was possible for her to get madder than before, but she did and he just looked at the floor sheepishly.

The mirror is only there to help you see through the lens, when you take a shot it's flipped up out of the way so this mark will never affect you photos.
Sorry if I'm telling my granny how to suck eggs

I'm not sure where this issue about reliability comes from. I've had my K-7 since Jan 2010 and so far I've taken over 80,000 pictures with it.
Tempting fate here... It's never let me down, Pentax say it's good for 100,000 actuations and I'm closing on that fast.
Keep the faith get a K-5

It does depend on the sport, if you are talking motorsport apparently its slow to focus, this is the reason I went for the Sigma 70-200 f2.8.

Do I detect lenses envy?

Lovely colour water .... Not!
Love the second pic and a good job done on the panning.

I hope you have better conditions than we did at Barry on the weekend of the 11th/12th...flat calm. They picked the wrong weekend as the tide was too far out and once it started to flood the beach is so flat the action was miles away so I didn't bother to hang around.
Far better to have held it the weekend before or after so the tides would have been in and the action nice and close to the shore. If you have a bit of a lumpy sea the action is spectacular. Take a long lens if you have one I used a 600mm Sigma F8 mirror last year and got some stunners using catch in Focus.