We had a crappy front door which leaked air with the smallest wind gust. I bit the bullet and decided to replace it with a new door from HomeTech.
The new door is very good looking. More importantly, it seals properly. No more cold air drafts. As a bonus, it also provides good sound insulation - I wasn't too concerned with noise but it is nice to have such good sound-proofing. The 3-point lock is surprisingly nice to use - I had to slam the old door to get it properly closed; this one closes with the slightest push. No more door slamming. I've had the door for several months now and it still functions exactly the same. No sagging, no movement in the frame.
The crew of two guys worked very conscienciously, took their time (as far as I can tell, they took twice the time they anticipated to do the job and did not bat an eye). Having had my fair share of experiences with lousy contractors, I was relieved that these guys were good at what they were doing and did not take shortcuts.
I will be using these guys again this coming year (for the back door and maybe a window).