Is a 6 hour layover in Edinburgh enough time to get into the city (Apple Store) and back to the airport in time for your next flight? If so, how do you recommend I get to the city and back?
Everything you need to know is on the airport's Transport Links. The short answer is yes, easily.
The fastest, but most expensive, way is just to take a taxi. Follow the signs to the taxi rank, should take around 20 to 30 mins to get into town and budget around 25 pounds one way. You can pick up any black cab on the way back.
Trams are 8 pounds return, run every ten minutes or so (officially every 8 to 12 minutes) and go down Princes Street which I'm guessing is the Apple Store you wish to go to. You can get off on the terminus or just after it turns off Princes Street. Journey time is around 35 minutes.
Similarly the Airlink bus is 50p cheaper, takes about as long, runs about as often and stops at Waverly which is a short walk.
There are local buses that are much cheaper, but they take a long route and stop a lot, I doubt it's worth it.
So, even if you want to get back to the airport two hours before departure you'd still easily manage two and a half to three hours in the city. Time enough to go shopping and grab a bite to eat.
Of course you'll have to clear security when you return to the airport, and this can take a looong time during peak hours. They've redone the security area so it's faster now but it can get very busy. Also if you're pulled over for further screening you may need to wait in a queue for that. Basically I wouldn't try cutting it too close.
I'm also assuming that you can legally enter the UK.
The Edinburgh Airport website has a page on Transport Links with details of several options to get you to/from the airport. The public transport options include Taxis, Buses, Coaches and the Tram. Assuming cost is not an issue, here are indicative journey times into the city centre using the different means of transportation (the Apple store is next to Edinburgh Waverley train station which is right smack in the centre of the city), quoted from the linked airport website:
- Taxi: ~25 minutes
- Buses/Coaches: ~30 minutes
- Tram: ~35 minutes
Being conservative here we can say that you'll need 1h to go through customs and pick up any hold luggage from the retrieval area, and 2h to check-in and drop your luggage on your way out of EDI. Leaving 3h for the return trip to/from the Apple store. The endeavour would therefore seem feasible.
When it comes to the dis/advantages of the different means of transportation, an obvious one is traffic which will inevitably influence your total journey time. This is especially true during peak hours. The tram on the other hand runs on dedicated roads for part of its journey, and therefore the journey time shouldn't be hindered by traffic as much. It is also worthy to note that the route to/from the airport has some bus lanes, which can be used by taxis too, that can help avoid traffic.