Good to read some positive reviews here but my advice is to prepare for the worst if you ever have the misfortune to go through MIA in transit. Having read some reviews here I changed my return flight to a later one as it seemed that 2 hours would not be enough to go through immigration & customs. New arrangements provided for 4.5 hours. Well I'm glad I did. After a 15 minute run from the plane I joined a queue at immigration at 5.45pm and was finally granted permission to enter the USA at 7.30pm. Some people in my queue and those adjacent were pulled for questioning by officials after queuing already for an hour or more. Guess they didn't make their connections. The baggage bit was hopeless - despite being told that I would have to collect my bag and go through customs to clear it and recheck it it wasn't on the carousel (no signs telling you what carousel to go to - you just have to wander up and down and hope you can spot your flight). Piles of bags everywhere - some of them were from flights which had landed several hours earlier. The concept of customer service is clearly non-existent in staff at this airport: to get help I had to break up conversations between staff who would have quote happily chatted indefinitely looking at pictures on their mobile phones flirting with each other etc. if I hadn't forced my way into their conversation. Turns out that despite what my Air Jamaica people were told in JA my bag was checked through already (apparently) though the staff at my departure gate denied this. I did have to check in again at Departures and eventually arrived at my gate at 9pm for a 9.30 flight. Concourse E - dismal place rubbish facilities (hot dogs and a tiny Pizza Hut concession - and that's about it). My bag did reappear in London. I dislike Heathrow and UK airports in general but it seemed like a paradise of good signage helpful staff and logical transit arrangements by comparison. If I can avoid it I will never go to MIA again nor will I book flights requiring a transit at a US airport - nearly missed my connection on the way out at JFK because of a 50 minute wait for baggage and being misadvised about transfer of luggage to next flight from different terminal. But that's another story.