I'll rarely turn down a jumping flashbulb, so the Penetrator is certainly a mech I enjoy playing. Never been a huge fan of the art or the mini, but it has always been reasonably effective for me. You never get to use those pulse lasers as much as you would like, but they do offer a very hunchback-like deterrent that has value even when you aren't firing them. The ER Larges aren't bad per se, but they aren't great either, and the range is good enough that you can stay in the fight, even when facing faster opponents. The speed of this design, especially in the time frame is exists, is a problem, but the jump jets make it tolerable. Where something like a Rifleman or a Hunchback is just going to feel slow at 4/6 during the civil war, a 4/6/4 is enough to help keep up with the 5/8 heavies that are running around in that era.
By the time we get to the Jihad, I'm not sure it is enough anymore. I agree that Improved Jump Jets and/or Clan large lasers would have been great upgrades for this mech in 3150. You could have kept the IS Medium Pulse lasers so it wasn't totally optimized, and it would have made tons of sense as a refit. The snubbies, even with AES, are going in the wrong direction. Now you have a mech that is definitely slow for it's era, and it has the shortest ranged weapons of any variant. The 7D really needs a city or a dense forest that will force everyone to get in close, or it's going to have problems getting left behind and out of the brawls it wants to get in.
Lastly, I wanted to mention that this is one of those mechs where the Prime configuration is my favorite. Regardless of the era, if I have a choice I'm taking the original version.