Does the new adhesive Synthetic polypropylene underlayment totally take to place of using the ole asphalt-felt underlayment??

Is it becoming standard practice to totally cover the entire roof exclusively with the synthetic underlayment? I realize that it's much more costly to install the adhesivde synthetic underlayment, but it seems to be a MUCH better underlayment for the long run.

I noticed that the Synthetic underlayments don't have the horizontal guide-strips that the felt paper has...is that correct?

Thanks.

Your roof should be allowed to breath. Applying full coverage promotes sweating, and allergy growth in dark, wet, stale air pockets beneath.( both cause rusting of nails and deteriorating conditions ) Eccessive heat build-up in summer causes brittle shingles prematurely. Condesation freezing in winter expands pressure upward causeing pop-ups and lumping.

I personally reccomend useing it only on the eves ,rakes, dormers, chimnies, and any pennatrations, then fill the rest with breathable shingle underlayment not more than 15 pound.

As for the lines,....Because the underlayment bonds to both decking and lapping, adjustable pich, lap lines are not needed. 4 inch laps will do.