Is it so hard for White to hang onto the pawn? I think time control plays a big part. In rapid/blitz the initiative is more important, but at a classical time control, the accepted lines are not *that* difficult to play (or at least not as difficult as some say...). The critical line now is the accepted double fianchetto starting with 10 Rb1, which Kramnik used  several years ago to practically kill the Benko at top level. A few authors have expressed it to be difficult to handle as White (McDonald, Rowson, even Flear on Chesspub), but Cox recommends it in his upcoming book so its hard to say for sure whether this is the case. 

For myself i use the non-accepted f3/b6 lines purely for practical reasons, since the Benko is a rare guest to tournaments these days..they might even give Black some problems. 4. Nf3/6. b6 as recommended by Palliser is a very reasonable repertoire choice since it leads to typical Benoni-type positions which you really ought to be able to play well as White anyway.

An interesting line is Zaitsev's (1.d4 Nf6 2.c4 5 3.d5 b5 4.cxb5 a6) 5.Nc3!? ^ 5...axb5 6.e4 b4 7.Nb5, which can lead to inteesting tactical play and, at the very least, avoids Black's mechanical queenside counterplay in the main lines.

If that doesn't appeal (and I should point out that Black is in pretty good shape after 5.Nc3, last time I checked) 4. or 5.f3 are also quite interesting lines.