I took the lift down to the Underground, got a ticket, and hopped on the Tube to Russell Square. Anyone who has known me longer than a few minutes knows that public transportation is not exactly my forte, but I found the Tube to be very easy to navigate with many maps posted inside the cars and announcements at every stop. It was very clean and safe as well. Incidentally, the Tube is 150 years old this year!
The terminal where I got on was the first stop on the Picadilly line, so the cars were empty and it was easy to find a place for my luggage. Once we got to the South Kensington stop, it got really crowed inside the cars. By the time we got to my stop, Russell Square, I had to be a bit aggressive about getting my bag and getting off the Tube car. All in all, I would definitely recommend using the Tube. My only complaint is that I wish they had an express train with fewer stops. It took an hour to get from Heathrow to Russell Square, but I would still recommend the Tube for its ease of use, convenience, and cost effectiveness.