Grazy,
If you imagine all of the suspension setup being the same as stock - but the spindle part (that's the bit that has the brake rotor & hub on) being a few inches higher - the net result is that the bus sits lower but the ride quality is the same as stock.
It does have some minor drawbacks though:
1. Dropped spindles aren't available for all years of bus (generally speaking drum brake models are OK).
2. It can increase the width of the front track (but not by much) meaning that your wheels will stick out more - this is one of the reasons that they are commonly seen on buses with narrowed front beams.
3. Early dropped spindles were welded instead of machined - not very strong and prone to failure (not a part of your bus you want to snap off!).
4. They are considered expensive - especially if you need a narrowed beam too.
5. You can't adjust them, if you get a 3" lowered set of spindles then your bus goes down by... 3"!!! If you use an adjustable beam too then you can still make minor adjustments to get things just right.
In short, a bloody good idea - get the best you can afford from a reliable company!
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)