We have been to WDW (for 8-10 days each time) at least once a year for the last 5 years. While we may not be quite the experts that some people are, I would consider myself to be *well experienced*!
We went to DL last November and stayed at the DL Hotel for 4 nights. We went into this trip KNOWING full well that DL is different from WDW and that many people feel "let down" or disappointed by DL after visiting WDW.
We had the BEST time at DL! We loved everything about it (except for the fact that we became disoriented a few times, because it's definitely set up different than WDW

). We were there for Small World Holiday, and Haunted Mansion "Nightmare Before Christmas". Both incredible! We really enjoyed comparing the attractions that are similar to those at WDW (I say similar, because even though the NAMES are the same, the attraction is definitely different). The DL *winners* over their WDW counterparts were:
Indiana Jones (hands down, NO COMPARISION!)
Pirates.....gotta LOVE the whole Bayou effect (and the restaurant as well)
Small World (had the Holiday thing goin' for it)
Haunted Mansion (ditto)
Space Mountain....better ride at DL
Autopia (vs. Tomorrowland Speedway)
Treehouse (Tarzan vs. Swiss Family)
Tiki Room (sorry, the original is better....)
Big Thunder Mountain......
PLUS you get Roger Rabbit, Alice in Wonderland, MR TOAD!!!, Pinocchio's Daring Journey, Matterhorn (rehab while we were there

) Casey Jr's Train, MR TOAD!!!!!, Storybook Land Canal Boats, Davy Crockett Canoes and oh yeah, did I mention MR TOAD?!?!?!
The one and only attraction that was a unanimous *winner* at WDW was Splash Mountain.
THEN....you get DCA! If you like Rock 'n Rollercoaster, then you'll love California Screamin'!!! WHOO HOO!

And Soarin' Over California, is (as previously mentioned) the most outstanding attraction Disney has ever offered. Great redwood forest-inspired play area, that is SO much more than a playground...more like a physical challange course! Grizzly River Run is quite similar to Kali River Rapids....just beware of the *moving* cars on the Sun Wheel....TOTALLY FREAKED ME OUT!!
We were at DL/DCA for the "5 days for the price of 3" deal....and we spent 4 very full days at the parks. We enjoyed every minute of it....although I would have to admit, that if we weren't staying on-site there, the whole *Disney Magic* feel would have been lost for me....as you definitely are plunked down smack in the middle of urban Aneheim!
Oh - and while in So. California, we went to
LegoLand as well.....and Venice Beach, and downtown LA....loads to do in the area in addition to DL/DCA!