Really interesting comments here. For me it boils down to the following:
I'm really glad we have playtesters- the hobby seems (for me at least) getting more enjoyable every year with some great rule sets and armies being released- something for everyone I'd say, whatever style or taste. A big part of that is the time and effort GW have put in as well as the play testers themselves not to mention the community at large.
All the playtesters mentioned are all excellent players who spent years playing the hobby- this is what makes them great play testers as well as competitive players. I'd expect all the above names mentioned above to finish in the top standings regardless of whether they've playtestested a new book or not.
It's also playtesters hobby/passion and something they've invested a lot of (personal) time in despite working in other jobs/family commitments. I stress the time elements because this relates back to one of the many reasons why they are successful players- they shouldn't be penalised for this in the tournament setting or ostracized for gaining an unfair advantage in the 'meta' - they've given time, thought and energy for the benefit of all.
It's an awsome dice game and you can be as experienced as you like, played all the armies under the sun new or old but if the dice fail you on the day then it doesnt matter playtesters or not. There should be some trust from the community that the people play testing are doing it for the benefit of all - again there should be no penalizing in the tournament setting for this or ostrocising through social media outlets. Whilst I'm sure everyone wants to win ( I certainly do in the very few tournaments I enter!) the most important thing is that everyone has fun, meet some new people and have some awesome games with armies they love and not get too hung up on whether someone may/may not have a slight advantage because they've played a bit earlier with an army before its released. I stress that its about trust, trust that they're doing this for the community and we are all the better for it. If they play with an army I havent had chance to experience before then that's a great challenge for any general as well as a great opportunity to pick the brains of an experienced player and hopefully you'll learn something about yourself and your army in the process.