(1) God is atemporal.
(2) A tenseless theory of time is true.
Johnny-Dee had suggested that they are biconditional (assuming we are talking about theists): God is timeless if and only if time is tenseless. I disagreed since I don't think (1) commits one to any particular theory of time, and this is being discussed in the comments. I'm having difficulty with the comments over there today, however, so I thought I'd put my comment here as well, just in case. It's almost long enough for its own post, anyway.
"God exists now" is not the same proposition as "God's existence is tensed". The former only implies that "God exists" is true now. The latter implies that God's existence exhibits the same limitations in virtue of tense that the existence of temporal things does. Atemporalists shouldn't have any problem with saying that God exists now, any more than they should have a problem with saying that God exists with regard to any creaturely feature. God's existence is logically and metaphysically prior to the existence of anything He creates, so no matter what the difference between God and creatures may be, God exists. To suggest that God's duration is measured out according to a privileged temporal present, however, is a very different thing, requiring a very different (and rather difficult) set of arguments before it can be established.
As Xavier implies, it's fairly common among atemporalists to deny that the relation of creatures to God is perfectly symmetric with God's relation to creatures: in a sense the relations of creatures to God all partake of the limits and nature of creatures, whereas the relation of God to creatures partakes of the attributes of God. Or, in other words, creatures are related to God in a creaturely way (tensed, if creatures are tensed) and God is related to creatures in a divine way (eternal, if God is eternal).
Incidentally, with regard to Johnny-Dee's original point, I think there is a significant issue on which tenseless vs. tensed theory of time will affect one's view of God and time: someone who believes in a tenseless theory of time will see eternity as a rigorous analogue of omnipresence, while someone who believes in a tensed theory of time will at most consider it analogous in a more loose and indirect way.