Just came across this blog post and found it helpful in summarising most of the arguments into the one spot! Also check out the comments for a cheaper option!
http://www.themadfermentationist.com/2013/01/beer-gun-and-counter-pressure-filler.html
Very good - I hadnt seen these products from MoreBeer before.
I second that about chilling/freezing the bottles.
As an owner of the Blich-beergun, I think I will buy the counter pressure one - looks brill.
Sorry Brian !