I really enjoyed it - reminded me good old times filled with action, mysteries, experiments gone wrong and excitement. It had fun, shocking moments and happy ending - is it all we want? The only thing I think may be said bad to this episode is, that there was nothing too original. We have seen bad guys cloaked to invisible and making a lot of destruction (like the on in alpha site).. or people disappearing to other dimension (like the all noticed: Cristal skull)... so, in so many ways it felt for me that they wanted good and little funny, positive episode with all the things we used to love, so they took little from everywhere and put together it.
I cannot say it was bad.. :)