It's unsound. Aside from that there's nothing wrong with it, besides everything. How many GMs have you seen playing it lately in serious games?
BUT, I used to play it routinely OTB a few decades ago vs 1.e4 with very good results, in fact I went from USCF class-B to class-A with that and another barely sound opening - the Budapest Defense vs. 1.d4. You can probably get away with the Latvian OTB until you run into someone who knows just one of several very good lines vs it (that you don't) and disillusionment might start to settle in, but maybe not.
If you plan on playing it routinely this is one opening you should seriously considering purchasing a book about
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=latvian+gambit
http://www.chesscafe.com/text/kaiss44.pdf
http://www.chessville.com/instruction/Openings/elburgc40.pdf
I have played a few games using this opening and tried a few variations and I have fallen in love. What an opeing. I'd love to hear your thoughts and comments on this intriguing, tactically rich chess opening.