My roommate downloaded the PDF of The Book Of Erotic Fantasy onto my computer. It's available on isohunt.com for those of you who are interested.
As I thought, there are a few gems to be found in that book. There were some parts a skimmed through but didn't care enough to read fully. And there were some things that are strictly a matter of taste.
The feats that boost your stats through sustained sex are interesting (and useful). In using those feats, the rules on sustaining sex are very important. The rules for seduction are different from mine (they use the Diplomacy skill). And some of the spells and classes are kinda cool. Like the Tantrist Mage, who recharges his spent spells by having sex for one hour. Or the Sacred Prostitute, who can heal people by having sex with them, and even recharge another spellcaster's spells with sex.
The "Cursed Orgasm" spell can have some clever uses (cast it on someone covertly then seduce them). The "Disrobe" spell can trip someone up during battle (kinda hard to fight when your armour is falling off). "Touch Me Not" grants a +2 to your AC, and inflicts 1d8+1/level (to a max of 1d8+5) damage/round to anyone you're grappled with.
The STD, "Whore's Delight" can actually be a very useful tool. Get infected, sleep with the enemy, if he fails his Fort check he's paralyzed for 1d4 hours. Need help convincing him to go to bed with you? Black Out has a Fort DC of 20, is relatively affordable (only 25 gp), and makes them suseptable to sexual suggestions (like from a "Suggestion" spell).
Of course, there are several things in there not worth adding. But that's the kinda stuff you just ignore and choose not to use.