T5 rocks
T3 to T5 transfer was easy 3 weeks ago on my flight to Geneva - though the coach does take about 20-30 minutes.
T5 Rocks! BA lounge is especially nice.
I was on the ground just over an hour - my bag didn't make my flight to Geneva, I had to hang out for the next flight an hour later (Geneva is not a great airport to spend time in). Not sure if that was a T5 issue, but there ya go.