What is the difference between Heathrow Express and Heathrow Connect? I think they travel the same route, but connect makes local stops and is 10 minutes longer, yet takes the same route. Connect is also cheaper.

Can I as a tourist take Connect, or must I take Express? I heard somewhere that Connect is only for airport employees, etc.

Leaving Paddington, I heard Connect is not even listed as going to Heathrow on departure boards.

Express is 15 minutes. Connect is 25. How long is the Tube?

anyone can take Heathrow Connect, a local train that stops a few times en route to Heathrow -unlike the non-stop Heathrow Express.

Yes i've heard that since Heathrow Express also runs Heathrow Connect, they don't highlight it at Paddington because they wish to funnel tourists onto the much more expensive Heathrow Express.

Tube takes about 40 mins from central London i believe - but i'm not sure if the construction near the airport of extending the tube to Heathrow's soon to be terminal 5 is finished - last Dec there was a bus link from Hatton Cross tube station to the airport, taking a bit longer and a bit more cumbersome for those with bags. Advantage of tube is you can board anywhere in London - negatives trains can be very crowded at times so with luggage and having to change to the Piccadilly line with bags can be a hassle. There are also airport buses and airport transfers that can be surprisingly cheap and have been discussed ad nauseum on this forum.

The tube now stops at all four terminals. HEX takes a shorter amount of time than the Tube and you pay for that speed and "convenience."

Connect is slower so you pay less.

And there's another route from Heathrow that goes to Waterloo station (eurostars to Paris/Brussels go from here) that i took last year to go directly to my Eurostar train to Paris.

Take the airbus from terminals 1,2,3 unified coach terminal (not from 4, take Heathrow Express in airport to terminals 1, 2, 3 unified tube stop. Take this bus to Fletham train station, about only a mile from terminal 4 actually, but the bus takes a roundabout route around the airport, stopping at some hotels en route. At Feltham there are very frequent trains into Waterloo station. To me an easy way to reach Waterloo with luggage and not too many hassles.

The Heathrow Connect train stops at Hayes & Harlington, Southall, Hanwell, West Ealing, Ealing Broadway and London Paddington. At Ealing Broadway, it connects with the District and Central tube lines. Between Hayes and Paddington, normal tickets, including Travelcards, are valid. Thus, if you buy a one-day Travelcard for zones 1-6, you only have to pay for Heathrow Connect between the airport and Hayes, so it can be a lot cheaper than Heathrow Express. On the other hand, it's still a lot more expensive than getting the tube from Heathrow, or taking a bus to Hayes from where you can use a Travelcard to Paddington.
Note also that the Piccadilly Line tube from the airport runs every five minutes, Heathrow Express runs every 15 minutes, and 'Connect' runs every 30 minutes - so will usually entail a longer wait.

Besides Geoff Hamer's excellent info - don't just compare 15 or 25 mins for the train vs. 40-45 or more for the tube. Taking the train all the way in only gets you to Paddington - which is fine if one wants to be near Paddington but isn't great for most visitors.

If you are heading into very central London, the tube is probably faster. Waiting for the next train, traveling to Paddington, queueing for a cab at Paddington (or taking the tube or a bus) and traveling on to the final destination usually takes more time (and costs a LOT more money) than simply taking teh tube all teh way in from LHR.