For single player - I love this shield
For PVP - I despise it.
Permanent control is usualy a must in order to beat a deck with multiple copies of Ps.
That means that this single card counters mono- Earth, Life, Light, Water, Air, Time and and Phase shieldless Aether (though theres few of those) Death decks may be able to bypass through poison but it's still a very serious damage reducer. Enthropy has the destroy ability, which again is a rare enough card in PVP. Gravity has momentum and many momentum decks (again rare) are built solely to counter Phase Shield reliant decks. Fire and darkness are great against it, pulvy too but then thats about it (I'm excluding all rainbow decks, which regardless probably wouldn't have more than 3 Perm controls). And now heres my problem; PVP is largely dominated by Fire, Darkness and Aether decks. I think that this domination revolves around this one card. Now, I know that there are many other fantastic reasons why these three are great PVP'rs and that if it wasn't this permanent it'd probably be some other permanent I'd have gripes with etc. But still.. I think PVP is hampered by lack of variety and that this card (or the lack of other elements ability to deal with it) is the root of the problem.
Sorry about the long rant.. I just got pwned by a Phase shield deck