Portable hell
Its just plain Doom in portable version. Even though a lot time has passed its still great and addictive especialy when you can play it while on bus or anywhere outside your home.
Graphhics and sounds are similar to original that may be negative for some people but its suits well gba making it best fpp on this portable system (duke is nice too but it lacks something and controling is harder). Doom is good port but its lacks bonuses and specials that would make old time players squeeze all juices from the game. If you own Game Boy Advance and like good games you will love this one and sink in it . I noticed it you can't play just minute or one level you want more and more its so addictive.
Are there any cons personaly i think no, maybe just one thing thats not quite connected to gba version. If you own Psp you can play original Doom and all the free mods downloaded from internt just with one homebrew aplication and after that Gba versions may be not enough.