No company will claims their products are worse than competitor I'm a D90 user and have same problems as you. D90 and D3100 have same ports so I assume the GPS units which can work with D3100 will work with my D90. I'm struggling between Solmeta geotagger Pro and foolgraphy bluetooth GPS. Solmeta Pro is the only one camera GPS I found with LCD,internal battery,electronic compass(provide heading information), memory card and has "indoor lock" functions, all of these features attract me. The price is under $250, I think it worths. The foolgraphy stands for its bluetooth, cableless looks cute and smarter, however it doesn't include all the functions that Solmeta has. So bluetooth or wired GPS, I need to take more time to make a decision.