The sharp acceleration curve certainly helps but when the player first starts It needs to snap up to a minimum speed. The acceleration is great at higher speeds but I don't think the player really needs to walk that slow at the start of the run.
The spin dash and other acceleration methods can help to make the levels flow better and reward skillful play for knowing when to use them and having the risk-reward of burst speed. The drill dive helps but if there are no slopes around or slopes are in awkward places for speed it can be a trouble to use. I feel the Drill dive is a tool to help retain momentum in situations when you need to move directly down, perhaps from a standstill. I see it more as a momentum preserving move rather than momentum gaining. as you are unlikely to use it from standstill.
From standstill the most effective way to get going is to run the opposite direction then mach turn as it gives you a massive boost in speed for some reason