I'm running with this little guy in a campaign at the moment, and I must say I like it. The 5T isn't oversinked; it's perfect. Heat neutral exactly on a jumping alpha is just what the doctor ordered for a small, fast harrasser. If you're playing him right, this guy doesn't do enough damage to warrant being an important target, but he's useful enough to tip that battle with his pinpricks and mobile ECM bubble. If he were more deadly, he'd be a target. If he were slower, he'd be a target. If he were more lightly armored, he'd be a target. Fortunately, he's none of the above.
My only gripe is the range. A 15 hex main gun just doesn't cut it in the post-Clan Invasion battlefield. If I had my way, I'd swap the standard Large Laser for an ER variant. Keeps the heat low enough to be workable (+4 on a jumping alpha), but adds some much needed range to the main gun. Total energy weapon loadout means it's A) completely ammo independent for those long-term campaigns and B) invulnerable to ammo explosions. Sure, the XL engine makes him less survivable than otherwise, but the gain in speed and weaponry is well worth it, in this case.
My rating: 8/10