Once we got through the Disney gates we just followed the signs to each park - we didn't find it difficult at all.
We were very close to the Downtown Disney gates, but for MK and AK it was quite far, because we either had to pick up I-4 West and go that way, or we had all the traffic lights past DTD to get through (which adds more than you think to your travel time).
The thing with MK too is that first you have to park, then you have to get from your car to either the monorail or the ferry (at the TTC), then you have to travel across the lake, then you have to walk to bag check, then get through the turnstyles. It actually takes quite a lot of time on top of just driving. I would budget for at least 30 minues.
And if you're hoping to get into the park AT park opening, I'd aim to be at the bag check by 8.45 at the latest - 8.35 might be better, depending on time of year (peak or not). So that has you leaving the hotel between 8 and 8.10. We misjudged timing on several days, and got to the parks 10 minutes after we'd wanted to, but luckily it didn't end up mattering too much b/c it was a non-peak time. But if it's peak time and you have a "get to park at opening" strategy, then I'd be leaving the hotel no later than 8. The advantage of early too is that you get a close parking space, and you can walk to the TTC easily instead of relying on a parking lot tram.
Luckily for us we are early birds, and can easily be ready by 8 a.m. I know some people would find that very difficult!