[ACBlinky]

Pros
48" length gives you lots of lighting options (it can be tough to light a 30-36" tank), and at only 12" wide, any light you choose should brighten the tank from front to back no problem.

48" x 23" is a nicely proportioned viewing window

65g is a good size - lots of options when it comes to fish

At only 12" wide, the rockwork won't be very deep, so you'll likely see more of your fish (I have small fish that seem to be able to spend minutes cruising around inside the rock before they come out again, because it's 14"-16" wide in places and runs the entire 48" length of my tank.

Cons
12" width can be challenging to aquascape - not impossible, you just need to be creative

The front-to-back dimension can also be a hindrance when it comes to corals - most tend to grow in all directions, and 12" isn't much room for, say, a large LPS coral or an anemone to expand.

If you install an overflow, in-tank skimmer, large powerheads or other equipment, it can feel as though you're losing much more usable space than if the tank was 18"+ wide.

Your stand (if it's a factory stand) will probably only be about 10" wide inside, so it will be tough to fit a sump or equipment - you might need a custom stand, or you could set up a refugium beside the display rather than underneath.

HTH