The speed of expansion up to Turn 6 is just as fast as any other fast expanding nation baring an instant SC (Like a Fire Dragon). After that, the cheapeness of Rangers and high production of Ulm making your 3rd and 4th armies, to hyperexpand will outpace most other nations, especially when you throw VC into the mix after turn 7-8.

In a good starting position I've had BF Ulm expand without a SC as fast as one with a Fire9 Dragon until they reached that cap then they surpass it.

In a bad starting position they do less well, but better than other nations who cannot mass xbows (Thus they can take Heavy Cav provinces if they want to risk it and know what they are doing).