I've been to this lounge about a dozen time by now as an expat in the ME, will leave my opinion here in comparision with Peral Lounge (mainly for biz class passengers of TK, EY, EK, BA etc.)
In terms of food quality, bar, lightings (atmospehre) and others, GF new biz lounge is uncomparable to Pearl lounge which exceeds in most of aspetcs. Neverthelous I high apprecaite quite genune, friendly, kind hospitality of receptionsts and lounge staff at Gulf Lounge (in comparision, Pearl lounge receptionist girls are sometimes bordertline rude and unfriendly) in most of time.
As for Shower facilities, I don't know why but whenever I visit Pearl lounge, shower faciltiies are alwasy in maintenacne (now I even doubt it's most likely intentional), which is a big turn-off to me(female passenger). I used GF shower facitlies a couple of times since its opening, surely it's not the ones like EY in AUH or TK in IST lounge shower facilties, but well... better than nothing. For female passenger, please take your own "shampoo and conditioner" (conditioner is not available/given) if you plan to take a shower in this lounge.
Lastly, one day I had a connection at BAH (arriving by GF Biz but departing by TK biz, layover about 9h) and I was accepted to netierhr GF lounge or nor Pearl lougnes as Pearl lounge only accepts 3 hours before departure (a very strick policy). So if you have a long layover in BAH, please consider that.