The only problem i experienced was that Hammer, when i had Spirits FGD file loaded, wouldnt display the Opposing Force entities, and vice versa. Mergin them seems to have let me view both of them, and through this is can run them in my mod (with a little bit of editing of the games coding of course - converting everything to ASKII helps as well, but i wouldnt advise doing it if you dont have the correct software eg.
"Spectra Proggraming Pack" or CPR Industries Patented - some russian word that i find difficult to translate into english, as its in russian symbols - so i shall write it down as it sounds "Der's progaf schesk". I tried copying and pasting the Russian symbols at work, but they came out as a series of squares, which wont really work in you translation.
PS, i can translate Russian vocabulary into spoken english and vice versa, but when it come to the Russian symbols, i can write in them, but i cant translate them, as there isnt really an english equivilant - and a Russian/English dictionary is rather difficult to come by here in the middle of Russia...
PSS, i am going on a business trip tonight, so i shant speak agian until monday, please exscuse my abscence - least there isnt any nightshift on business trips, just lots of Vodka and cheap cavviear