I did the T5->T3 transfer this week and it's horrible! When you arrive at T5 you have to use the horrid transfer bus to T3. It was packed with people standing trying to manage their bags. The route takes you the full length of T5 A gates, then back along the far side of T5 B gates before you enter the tunnel to Terminals 2/3. On arrival at T3 you are dumped a good 10 minute walk away from the Flight Connections Centre and mixing with other arriving passengers. (Interesting to note - no one has checked your boarding pass at this point so i could have continued to T3 immigration had I wanted to. Of course, any bags would have been delivered in T5) You then go down two floors to the new Flight Connections centre. There is a Fast Track queue and the normal line was very long. You then walk past the airline desks before entering terminal near the AA/VS lounges. All around 30-40 minutes and I am a fast walker. Would recommend avoiding at all costs.