Hi Kerri:
I was just in Reykjavik in December, just for 4 days on the way to Europe.
And I think one day there would not be enough.
I easily filled four whole days; but in summer you would want to get out and into the countryside.
I loved it!; even though it was winter, and only light for 4 hours each day!
Very nice people, food was very good, lots to see in the city; plus I took a N. Lights tour one evening, and a whole day tour of the Golden Circle another day. And a free walking tour of the city.
All well worth it.
Iceland is very expensive, esp. restaurants and hotels; but if you stayed in an apartment, you could at least eat some or all meals there.
Grocery stores were fairly reasonable, but with limited choices, not like home, just different.
IcelandAir from YVR was just fine, no more or less room than other airlines, very clean, and I brought all my own food, as you have to buy it on board otherwise.
Everyone else seemed to do the same.
They do give you tea, coffee, juice or water.
The flight arrives very early: 06:15; and you can book in advance or on board for a GrayLine bus transfer into Reykjavik.
The airport is 45 mins. drive from the city.
Hotels are aware of this, and mine let me in at 08:00 and gave me breakfast when I arrived.
I stayed at the Hotel Orkin; basic, but clean and warm, and affordable by Icelandic standards, and a free breakfast.
You can walk from there into downtown in about 20 minutes; longer for me, as I have terrible knees.
I took city buses a couple of times.
Let me know if I can help with anything else!