No, its not bad, but if I were flying a 109 or 190 against myself in a P38, the 109 or 190 would win every single fight.
Maybe I've just gotten used to being able to do certain things that the P38 just doesn't do well. I was flying a sortie a bit earlier and a Spit chased me around. The only thing you can do with a Spit within 3.0k of you on your tail is run. I couldn't make the guy overshoot to save my life, he shot off one of those little tails in the back before I ran away for good.
Then I bounced an F6F that was vulching, I had to hose him for about 4 seconds before he exploded. I'm used to diving in, taking a quick shot, and the enemy dies. Then I had several planes chase me around for a while, but they all go bored and went back to vulching.
After the enemy had captured the base, I was flying around and ran into another Spit. Again, the only thing the P38 seems to do better than a Spitfire is run. Couldn't turn well enough to get into a position for a snapshot, couldnt rope-a-dope him, I did manage to get on his tail once but he just went into a downward spiral I couldn't follow. Another F6F decided that the Spit needed help, so he jumped in. I ran away, but the P38 doesnt run away well enough, so I only got about d1.2 from him (where he was taking potshots, and HITTING). I ran for a little while, he gave up so I turned around to try again. We met in a HO merge, I pulled straight up at about d650 (I was going 300 mph), he pulled straight up behind me and shot out an engine in a snapshot. Then he ended up on my tail, where I again tried (unsuccessfully) to barrel roll to get him to overshoot. The move works about 90% of the time in a 109 or 190, it works about 0% of the time in the P38.
I guess I'm just hopeless as a P38 pilot- I can't see anything I like about the plane besides its ordinance load, and since you likely won't live long enough to deliver it, that doesn't count.