Hmmm, interesting. I work at an airport which has had more than its fair share of level busts. Most of our SIDs have stepped climbs. It is interesting to see the warnings published on 'third party plates' compared to the one on the UK AIP plate:
Warning Stepped Climb. Due to interaction with other routes pilots must ensure strict compliance with the specific climb profile unless cleared by ATC.
That to me means that you can comply with all the stepped climbs in the SID. Yet the example quoted by CosmosSchwartz with the word 'initial' can be misleading. Where's this from BTW?
I would expect a pilot to comply with all the stepped climbs in the SID unless specifically told to maintain an altitude before departure as we sometimes have to do.