So i'm looking for scopes for my AR, and i've seen a few that i like.  However i'm curious about the fixed vs variable debate.  can i get a few opinoins on say 2x, 4x and like 3-9x?  is it worth it to spend the xtra money on variable powers?  or is it based upon the intended use of the rifle?
Thanks.

Based on intended use.

In general terms a fixed scope is usually cheaper and a little more rugged than a variable.  Less parts and fewer things to go wrong.  Variables are more flexable in use.   Intended use will influence what power you should select.  My Wife runs a 1X4X24 in 3 Gun.  1X for close, fast stuff and 4X for longer targets.  I use a 3X12X44 for long range shooting on my varmint AR.  I use a fixed power, 1X Aimpoint, if you will, on my 3 Gun AR.  Most fixed power scopes I've seen are in the 2 to 4X range.  3 or 4X would be a little hard to use for close, fast stuff IMHO and not quite enough for beyond 250 yards or so.