Other companies offer passive 3D, although any TV that uses passive 3d will have an LG produced IPS panel as LG Display owns the tech for passive (Vizio, Hisense, Toshiba, Sony, and Panasonic all have contracts to buy passive 3D IPS panels from LG Display). As IPS panels, they will have similar shortcomings to the LG sets, although the implementation may be different with other brands that could provide modest improvements. As of now, Samsung and Sharp have decided not to buy passive LG Display panels and they have yet to introduce any other type of passive 3D technology and I have not seen any announcement that they are officially developing it (and LG Display has so far not licensed the technology out to anyone). In any case, there are no passive 3D sets announced for Samsung and Sharp for the 2013 model year so you will be waiting quite a while to see it, if it ever happens.
I look at multiple review sites to see various opinions. I try not to go by just one source as it is amazing how much bias and personal preferences color reviews even in supposedly professional reviews. At least some of the data is useful, although that also needs some care in considering, given that different testing methodologies can make a significant difference. Among sites I look at are:
televisioninfo.com (look for the archived versions of reviews here as now that they have been bought by a different company they are giving out resummarized versions of reviews that aren't nearly as good)
hdtvtest.co.uk as a European site the model numbers are different so you have to figure out what TV corresponds with model numbers from other countries
digitalversus.com Again a European site that uses different model numbers