We plan to make a lot of use of them since we wont have a car. Are they really so slow it can take 30minutes to get to a park? people have told me to leave an hour and a half if I have a dining reservation at another resort as well
Depends where you are staying and which park you are going to..remember WDW is the size of Manchester!!. Also, some resorts have several drop off points e.g CBR has about 5 so depending which section you are staying in ,it can take a while even when you get back to your resort.
The buses run frequently - don't forget there are also monorail and boats
Overall, I think WDW transportation is excellent
1997 - Newport Bay Club -DLP
1998 & 1999 - Disneyland Hotel & Sequoia Lodge- DLP
2000 - Caribbean Beach Resort WDW
2001 & 2002 - Newport Bay Club -DLP
2003 - Hotel New York - DLP
2004 - Grand Floridian - WDW
2005 - Hotel New York - DLRP
2006 - Grand Floridian - WDW
2007 - Yacht Club - WDW
2008 - Disneyland Hotel, DLRP
2009 - Yacht Club WDW, HRH & BLT
2010 - Beach Club WDW
As Debbie said, it really depends on your origination and destination points. On average, the WDW buses run about every 20 minutes--sometimes a bit more frequently.
If you are traveling from resort to resort, you will need to transfer at a park or DTD (strongly recommend a park). Typically, you'll grab the bus, exit at the park and board the next bus. But if you've just missed either of the two buses, you're adding 20 minutes at each location. Plus travel time. Then walking to your final destination from the transportation terminal. You can see where the 1.5 hours recommendation comes into play!
WDW encompasses something around 48 square miles. Never can remember if it's 47 or 48--close enough for our purposes. That's the size of a good-sized city!
Some resorts are located closer to some parks than others. For example, Pop Century is close to both EPCOT & DHS, so the bus trip usually is about 10 to 15 minutes. It's farther from MK, which typically is 20 to 25 minutes, depending on traffic. AK probably is 20 minutes.
And, as Debbie noted, you can combine bus and monorail or boat transportation, when appropriate. Again, you have to factor in time to wait for the next mode of transportation if you've just missed it.
Personally, I find WDW transportation works well. It can be crazybusy at park opening (or so I'm told--I don't usually manage anything that early) and park closing. Just relax in the park for a bit to minimize the wait time at the bus or other WDW transportation queue.
You'll be fine. You're on vacation! :D