I'm looking for dimmable light bulbs for chandeliers that won't exceed power requirements of the wall dimmers (typically 400W), which is pushing need for lower wattage bulbs in fixtures with higher bulb counts. I also want good light quality and adequate brightness. I find CFLs unacceptable in these applications, and was happy to find these halogen bulbs which are perfect 60W replacements. They make nice white light, have good brightness, are a good size, are instant-on and fully dimmable... basically everything I was looking for. The power usage isn't as low as CFLs but the difference in power costs gets smaller as bulb wattage goes down. Since I'm dimming these I expect them to last much longer than the full-power life rating on the box (true for incandescent bulbs, probably not true for CFLs.)
HOWEVER, out of 8 boxes (2-pack, 16 bulbs) 4 bulbs didn't work.... 25% failures right out of the box. These were carefully bubble wrapped to me, though I don't know what kind of handling they've had from the factory. I can't remember the last time I've found a dead bulb from the store, so I find this failure rate very unusual for an incandescent bulb. It makes me concerned about the reliability of the 75% that did light. Given the relatively high cost of these bulbs I'm obligated to try and exchange them, an additional hassle.
Update: Comments on problems submitted to the manufacturer have gone unanswered. Amazon rapidly replaced bad bulbs in first batch, and then bad bulbs in replacement batch, but unfortunately each of the replacement boxes had a dead bulb. I've given up on trying to get one box of 2 good bulbs, so returned the last box of dead bulbs for credit. All of those that lit are still working OK, so it seems that if they light they're OK. The only way to play this game is buy at least 25% more bulbs than you need (including spares) then plan to return all the dead ones for refund.
Update 5/18/2012: No failures out of a dozen bulbs, so they're lasting OK. Never did hear back from Sylvania.