Having been a runner for more than 12 years now, I have often run on treadmills for various reasons.
It can be safer than running outside, for example, if you need to do a run early in the morning or late at night. Sometimes weather conditions such as snow and ice make the treadmill a better option like has been the case for me here in Squamish at the start of the year.
While you should be able to run anywhere and it is a great way to explore new places, sometimes it may be better to run on your hotel's treadmill if you are unsure.
Whatever the reason, running on a treadmill has many advantages. You can keep track of the distance you've covered and the speed you're running at, you can choose to stay flat or tackle a few hills and your water bottle and/or a gels/energy bars are within reach without having to carry them.
Another benefit of treadmill running is that you can test your willpower. There is nothing stopping you from simply getting off at any point. When you are running outside, and you're a 30-minute jog from your home I suppose you could stop and walk home or take a cab - but it doesn't make much sense and is less tempting.
By contrast, a treadmill doesn't take you from A to B. So it is great mental training to do your workout as planned.
I've never owned a treadmill but have recently started doing some research on whether it may be worth buying one for at home.
During this winter, when bigger than average snowfalls made running outside next to impossible, I opted to become a member of a local gym. I have so far tried out two of their treadmills.
Mostly I have run on a treadmill by TechnoGym which I quite like. The buttons to change speed are very responsive and the surface is comfortable without being too soft. (I never quite realized how expensive treadmills could be, particularly those used in gyms and hotels.)
Speaking of speed, I don't worry too much about it in absolute terms. It is hard to translate the speed you run on a treadmill to your speed on the road, partly because of calibration differences and partly because of the lack of wind and of course the movement of the band.
I simply aim to run on the same treadmill so I can use the speed in that workout to compare with the speeds I did in previous workouts. Mostly I run on feel, ie if my running program tells me to do an easy run I simply play around with the speed until I find one that feels `easy' for me. Then in speed sessions, I crank up the speed as high as I can tolerate for the type and number of repeats I have to do.
I think you have to take the treadmill simply for what it is: a means to run when for whatever reason you are not able to do so outside. Don't worry too much about the specifics - just do your workout the way it is intended to be done, ie recovery pace, or a more intense pace as in a speed session, or settle into the speed you'll be comfortable with for your long run.
Then just forget about your ability to get off the treadmill, listen to music, watch TV, chat to the person on the treadmill next to you, or think about your running goals, the next holiday, etc. Sometimes it is very nice not to have to pay attention to anything else than keeping up with a moving band.
Going back to the research on purchasing a treadmill for home use, it seems that for the amount and type of running Tim and I do (7 hours a week for me and about 4 1/2 for triathlete Tim currently), it seemed that we would need something sturdier and more durable than anything under $1500 has to offer.
At a fitness store we visited last weekend the treadmills on offer were by Precor and PaceMaster. The prices of the treadmills on display varied from $1800 (the cheapest PaceMaster on sale) to $3500.
For our needs, it seemed that both a PaceMaster for $1800 and a Precor for $2800 would do the trick. But it is a large investment - and while I do think treadmills offer fantastic advantages, if possible I will choose a run outside any day. And I was able to do so this week already.
Some treadmill reviews are offered here: