While Rogues do have a few more skill points, if the Beguiler is serving the Rogue role in a party, he's going to (hopefully) max out Search and Disable Device. Yes, he's "limited" in skill points (fewer than a rogue, but as many or more than almost every other character in the game). However, since he's going to focus primarily on Intelligence, where a Rogue is expected to focus on Dexterity, he's likely to have an intelligence modifier that's at least 1 greater than the rogue, and possibly 2 greater (completely negating the rogue's edge). In any case, he can certainly afford to focus on Search and Disable Device if the party lacks another trapfinder. And his higher intelligence score will give him that bonus on Search and Disable Device checks.
Now, yes, the beguiler does lack some of the rogue's defenses against traps, and that will hurt him from time to time. Of course, the rogue's low Will save and reliance on melee combat despite being rather... fragile costs him from time to time, too. Traps aren't a beguiler's forte, just one of the many things they can handle well.
If a beguiler ends up dealing with a lot of traps, he might pick up two levels of Rogue, for the nice +3 to Reflex saves and Evasion. If he's not dealing with enough traps to make that worthwhile, that means that he's just as good on the trap front as a rogue would have been anyhow. And if he's dealing with that many traps and doesn't take a couple levels of rogue, it means he values what he can do as a beguiler even more.
Personally, I've played one beguiler so far (a Beguiler 6/Swashbuckler 3). A bit more martial than your average beguiler, he was actually quite capable in melee - slap on haste and greater mage armor (via an eternal wand), plus mirror image or displacement for larger fights, and he was quite effective. And that still left plenty of spell slots for useful things like dispel magic to knock out a similarly-buffed opponent's tricks, or spiderclimb to reach snipers... very fun character.
He also ended up serving as the party's trapsmith. Heck, with a couple of the items from the Magic Item Compendium, he could even dish out a few attack spells, thanks to thegloves of the starry sky and the goggles of the golden sun (essentially, sacrifice a 1st or 3rd level spell slot and cast magic missile or fireball, respectively at your own caster level, 3 times per day each). That never came up much, though launching a fireball into a group an instant after the party's warmage had also cast fireball on them was quite amusing. And, hell, he had a good UMD check and a couple wands and scrolls of Cure spells, just in case the cleric went down. Fantastic jack of all trades.
Right now, I'm considering playing a beguiler in a Pathfinder game myself, since the party is shaping up as a couple fighter-types (not sure on exact classes, but probably nobody with rogue skills) and a cleric. So, a party where a beguiler may be a perfect fit.
