As a comfort layer, latex in its softer versions has as many benefits as it does when used as a core material in its firmer versions. It can be purchased in ILD's from as low as 14, similar to memory foam, and it has comparable pressure relieving qualities to memory foam as well due to its ability to form itself to the exact shape of your body profile while you are sleeping, and to do this instantly as you change positions. Latex and memory foam share this ability to form a pressure relieving cradle more than other more commonly used materials.
Because even in the softer versions it has a higher resilience and is more "supportive" than other foams, it will also help support the more recessed areas of your body, such as the lumbar, that need "filling in" and are not in close contact with the firmer support layers underneath and because of its resilience it it less motion restricting than memory foam and changing positions and other movement on the mattress easier. This also makes thicker, and in some cases more pressure relieving, comfort layers possible when needed or preferable without the same degree of risk that a thicker "pillowtop" or "eurotop" comfort layer will put your spine out of alignment.
Its other main advantage is that even in the softer versions, it is more durable than any other type of foam and will both keep its desirable qualities for longer than other foams and is not nearly as prone to body impressions and premature breakdown. Durability is especially important in the comfort layers of a mattress which are subjected to greater stresses than other deeper layers.
There are many in the industry, including one of the largest manufacturers of Talalay latex in the world, who believe that in the very softest ILD's, Talalay latex that is made completely of NR (natural rubber) may not be quite as durable or resistant to impressions as the blended version of Talalay latex in spite of the fact that it would still have greater durability than other commonly used foams. This is because Talalay latex is lighter and less dense by nature than either Dunlop latex or firmer Talalay and in ILD's that are very low, blended talalay may be a preferable choice. Blended Talalay is also less expensive than natural rubber Talalay.
Talalay latex is the most popular as a comfort layer because it can be made softer than Dunlop and is more consistent in its softness across the entire surface of the mattress. Dunlop however is also used in the comfort layers because of its firmer and less "lively" nature which is attractive to some who prefer its feel. Latex is also the most breathable of all foams and this can be an important part of temperature regulation for those who tend to sleep hot. There are also versions of Talalay latex available that are specially formulated to help regulate temperature (Celsion latex is one of them) for those who need it however even the regular forms of latex perform very well here.
As mentioned previously, the only disadvantage of latex is that it is a more expensive material than other foams however because it can be very successfully combined with other less expensive core materials such as HD or HR polyfoam or innersprings, mattresses with latex comfort layers are available at very reasonable prices and in lower budget ranges if you know where to look and how to find them.
It is also worth mentioning here that many retail outlets will call a mattress a "latex mattress" even if it has as little as 1" of latex in its construction. This is completely misleading and is simply an effort to take advantage of the known benefits of latex as a selling point even though there may not be enough latex in the mattress to make a significant difference. Only a mattress with a latex core should really be called a "latex mattress" and even here the type of comfort layer should be identified in the "category name" given to the mattress. In general terms a mattress should always be identified by both the main material in its core and in its comfort layers. This type of misinformation is often not so "accidental" and some salespeople will "insist" that a mattress is made of latex when it only has a very thin, and possibly meaningless layer. Some of the very largest brands and retail outlets are "guilty" of this. This is why it can be very important to verify the claims of some manufacturers and retail outlets before you buy a mattress ... which of course we are happy to help you do in our forum.