First off--like other critical reviewers you'll find here, I also had major problems with the comb. This review was almost a ONE-star rating, due to the sharp tines and general design of the comb. This _extremely_ poor comb design caused me to stab my lip several times and also resulted in uneven trimming.
Like other reviewers, I previously owned a Norelco T980 and needed to move "up" when it would no longer hold a charge. With the T980 no longer available, it appeared that my options were either the QT4050 or the QT4070. Overall, the QT4050 is far inferior to the QT4070 in that it lacks the travel lock, quick charge, and turbo functions. HOWEVER...the 4050 has one feature that I believe was SUPPOSED TO BE included with the 4070--the "contour following comb". If you look closely at images of the two units side-by-side, you'll see that the comb design on the 4050 is closed--no giant gap and sharp tines with which to cut/stab yourself--and it also has a flexible guide. Those who previously used the T980 will surely recognize the design!
In my frustration with the 4070's comb, I did some research. Philips Norelco CLEARLY markets the 4070 as using their "contour following comb". That's not actually true for what's "in the box", however. The comb that comes on the shaver is model number 422203617701, which is their "plastic stubble comb". As it turns out, the combs for the 4050 and the 4070 are _interchangeable_, and with a phone call to Philips, I was able to get them to provide the 4050's comb--model number 422203617711.
After you get your shaver, if you're experiencing similar issues with the comb, call Philips at 800.243.3050 and ask to speak with a supervisor--first level reps can't seem to approve parts orders. Explain the situation, tell them you want the comb for the QT4050 (P/N 422203617711), and they'll send it to you, free of charge. Within a week, you'll be able to fully enjoy what Philips should have built in the first place!
For the record--after I received my new CONTOUR FOLLOWING COMB, the QT4070 is a FIVE-star trimmer--it's exactly what I wanted. The one-star ding represents the hassle it took to get this product to be all it should be!