Admittedly, only on my first playthrough, and only for a week and a half. But - without reading in advance to spoil the experience - I started a Cipher Beguiler, and have been very happy with both the power and the versatility. I think people are selling short the impact of Whispers of Treason in the early game - turning a 5 v. 5 battle into 6 v. 4 is huge. And Ringleader pretty much wins battles when you're swarmed by numerous enemies (such as some ship battles).
While an accuracy boost (as suggested) certainly would be nice for Beguiler (MOAR CRITS!), the extra range (20%) makes them able to open encounters from distance, and the focus regen when they hit something vulnerable to sneak attack (many conditions), gives them a ton of focus in most battles.
... and then when you get to disintegrate - wham. I'm using Frostseeker, which seems to replenish my focus quickly when I'm low. My only quibble has been lack of survivability, but that's on me, since I went 3 CON, 3 RES. In hindsight, I'd have balanced those more evenly with INT, since the AOE's don't have much radius anyway (yet - at level 13), so adding % to AOE radius doesn't help as much as with wiz/druid powers.
I do think Ciphers suffer from a lack of quality level 2 and level 3 (and level 7) powers. Level 1 has several good ones, and Pain Block is amazing for a support power at L4. Ring Leader @L5, And Disintegrate @L6 are boss. And Time Parasite sounds nearly OP from the descriptions in this thread (*drools*).
Obviously, not relevant to much of anything, but starting with 2 points in Mechanics and Sleight of Hand makes for much easier early-game $$, too. Farm those traps!