My two cents that will apply to whatever flat iron your go for, aim for one with adjustable temperature controls. Most irons that don't have gauges to let you control the temperature tend to go high around the 400s which is just way to terribly hot unless your hair needs that degree of heat.
T3 is a great brand that Sephora carries that makes flat irons with adjustable controls.
T3's Luminous 1" Tourmaline Flat Iron is $99 and is a more basic model, heating up to 410 with tourmaline infused ceramic plates which aid in combating frizz and aiding in amping shine in locks.
T3 also makes their Single Pass Professional Straightener for $160, this model heats up to 450 and also utilizes tourmaline.
For fine, damaged (dry, chemically treated, etc.) hair try to keep flat irons to the mid to high 200s, going no more than the low 300s.
For normal hair, opt for the 300 to mid/high 300 range.
Keep the high 300s for thicker, wavy hair and the low 400s for super curly or coarse hair types.
Always be sure to use a thermal protectant as well, find one that best suits your hair type to ensure hair won't be weighed down.
If you're open to shopping elsewhere, I'd suggest the Croc flat irons. They utilize ceramic along with tourmaline and titanium infused plates to smooth locks and have models that go up to 450. I've used both the Croc and T3 and like both very much (my hair is thick and wavy) but ended up getting the Croc as I snagged it at Sam's Club in a set for $80 (1" flat iron, carrying case, comb, and hair clips).
Check out the site Folica, there's so many reviews on flat irons and it's a great place to look up more info on hair styling tools.
I bought a ghd from Sephora about 7 years ago. It still is in great condition, and I have never had a single problem with it. My only wish is that it had a variable heat setting. I do love the auto shut-off feature very much because it means no more having to turn the car around and drive home to see if I remembered to turn it off
I have ghd. Its actually really nice. I used to use it everyday, traveled with it alot, but its still good as new
its very pretty too in its purple..
it makes my hair look silky and straight. but it does get really really hot...
I heard some really good things about the Sultra one but I've never actually used it. I personally like CHI and Hot Tools straighteners but I'm sure you'll find a good one. Sephora in my opinion doesn't carry enough hair tools really, and I think Ulta you'll find much better and less expensive ones.