I personally love Macs - if not just for the sheer delight of the sleek outside and polished interface. They do seem a little bit higher-priced than their Dell counterparts.
However, Macs tend to be more high-end than Dells, especially MacBooks, as they're basically a merge between the pro laptop PowerBook and the consumer laptop iBook. As a result, the MacBook includes a powerful dual-core processor, the Intel Core 2 Duo. It also has a built-in web camera, which may/may not be useful for you, but it's still a nice feature.
Another nice feature is the trackpad, which may look quite ordinary, except the right button is non-existent. However, it's got a very nice feature: put 2 fingers on the pad, and it suddenly starts scrolling whatever document is in focus, making the trackpad double as a scrollwheel.
All in all, I'm quite happy with the MacBook I purchased about 3 months ago - no problems or breakdowns with it (except the times when I messed with the kernel/partitions and it required reinstallation :D).
What you should expect in a Mac (MacBook in particular):
Elegant, sleek design
Easy to setup and use
Powerful processing insides
What you should not expect in a Mac:
Inexpensive or rock-bottom prices
Long battery life (powerful CPU sucks lots of juice)
Flexibility (no custom Macs or a lot of built-to-order options)
MacBook has lousy video card, so not really any good gaming
It's also worth noting that the MacBook has skimpy RAM (512 MB) and a small hard drive (60 GB), so you may want to consider upgrading these if you are going to perform memory-intensive operations or store a lot of data, respectively.
You should buy a Mac if you want a pro-sumer product to do lots of processing, but if you are only planning to do some simple web-surfing with it... you may want to get something cheaper like a PC.