Geg, I too play with BSP a lot. Some observations from me:
If your players like light, evasive mechs, then BSP is a tool for rewarding them. Since the BSP always run, they are starting at 6+ the light mechs evasion. Further, the light mech only needs to deal 8 damage to have a chance to degrade/destroy the larger tanks. So light mechs can go 'BSP hunting' in a way that rewards light mech enjoyers, as otherwise light mechs usually fall off in games with players opting for pulse lasers and special pilot skills (which BSP units dont get).
Internal balance on the BSP isnt great. I have previously posted about this, but in short the heavy tanks and infantry are pretty good, and the faster stuff is pretty bad. Part of this is the overall speed reduction... a Pegasus that moves 8 is a very different animal then a Pegasus that moves 12 for bringing its guns to bear, while a tank that moves 4 with a long range gun, versus a tank that runs 6, isnt much of a difference. The manticore in particular is really good for BSP use, as its 11 damage gun at 18 inch range lets you roll with a +1 on the chart versus other BSP units, it has a turret, and it has enough armor to require a few rolls to kill, unlike say the galleon.
The infantry are vastly better then by the book infantry with players fumbling through damage divisors and heaps of special case rules, but a swarm of 140 BV BSP infantry is still rough to grind through despite being far superior to manage vs an equal BV in 90BV total warfare infantry to grind through.