There are basically three conventional flat seats: herringbone, reverse herringbone (as in Sicma Cirrus) and staggered. Then there are original solutions like on BA or SQ. All flat beds have some advantages/disadvantages and are more easy to install on some aircrafts than others. For example DL chose three different types of seats on its 767, 777 and 747.

- I am in favor of the concept of herringbones because they give more privacy and much less noise. But they are not all equal and depend on the aircraft as the angle (direction of the seat) varies depending on the aircraft and can be more or less narrow. TG 77W (leased from Jet Airways) are wide and airy, DL 777 seats are recent, rather wide and minimize some of the criticisms addressed to herringbone (e.g. one can easily talk with neighbor). But your head is always far from foot traffic and the seat is wide at the head.

- I do not like reverse herringbones for sleeping because your head is near the aisle traffic and foot stomping. Others like it because it is more "airy". I have flown extensively the herringbone (old) and the reverse-herringbone Cirrus (new) seats of CX and prefer the old one, although it is a bit too narrow. The Cirrus seat is already used by US Air, CX and soon AA. They are not identical though, even if the structure is similar.

- I enjoy staggered seats if I can select one of the "good" seats (basically the feet of a guy behind you come under your armrest. Some of us have experienced the "single" seat on LX A340 and they are great. Every other row on the left of the A340 has a single seat (with arm/foot rest on both sides) while the next row has two seats with an arm/foot rest between the two seats. Those "single" seats are reserved for Gold *A.

But all those seats are flat and SO MUCH better than the current pair/trio angled seats.