I've played with my Romulans twice: once against Federation and once against Klingons. In both cases, my foe could anticipate the release of plasmas and were able to move outside of the 8" (in some turns, they were able to completely ignore the firing arc).
My current fleet is using entirely micro-machines so I'm playing with King Eagles, War Eagles and KR Heavy Cruisers. My last game was 850 points (2 King Eagles, 4 KR's). The Federation (1 Burke, 2 Constitution, 2 Kearsage, 1 Kirov), was able to stay in a tight wedge. As my ships approached, they just dropped the occasionally lucky shot on my cloaked vessels. Anyway, when I finally got in close, I decloaked on each of the Kearsages. That's when things went bad; Constitutions and Kirov did a full reverse so that my decloaked vessels were in the front arc. Then, the two Kearsages used all of their phasers to reduce my AD. Finally, the remaining plasmas rolled slightly low for damage. I NEARLY crippled both Kearsages (well, and destroyed the Burke, but that was little consolation)! However, the Federation was able to use their remaining firepower to take out 1 of the KR Heavy Cruisers. Next turn, as I decloaked my King Eagles to finish the job on one of the kearsages, I found drones, phasers AND photon torpedoes from the 2 ALMOST crippled ships destroying one of my King Eagles!!! So, after the second wave firing plasmas, I had taken out 1 Kearsage and 1 Burke, but lost 1 King Eagle and 1 KR. From there, I decloaked and tried to come around, but a 4+ Cloak turned out to be nearly useless (one more KR dead). Now, with 3 ships down versus only 2 down, I tried to come about, but the federation did an APTTE when they knew I could decloak and fire inside of 8". A few turns later, they even set up their last Kearsage as bait to let me destroy their now crippled ship only to take out 2 more KR cruisers. GRRR! I had tried to turn it around but with only 1 King Eagle left and they still had 2 Constitutions and 1 Kriov, it was time to go to warp. I really felt like I was playing against Kirk in "Balance of Terror" as they seemed to know when and where I would show up next. Perhaps, I could blame the slightly lower than average plasma damage, but I honestly think that poor playing and the 6" movement when cloaked really let my opponents know where I WOULD show up.