** This review is written from a novice's point of view ***
I have an EOS 350D with the kit lens and, despite being relatively happy with it, fancied extending the cameras abilities a little with a sharper and faster lens and, at the price, the EF 50 1.8 was the obvious candidate.
When it arrived I was amazed at how small and light it was, it really does feel like a toy and makes my 350D look a little odd with such a small lens. It's small size means you can literally stick it in your pocket so it adds to your "carry around" armory.
Initial results were disappointing - used wide open pictures taken of my young son indoors were far from sharp. However, this is down to me being a complete novice and not realising that taking close-ups using a 50mm lens at f/1.8 gives you such a small DOF that barely any of the subject could be in focus anyway.
Once I got the hang of this DOF malarky, my images suddenly became MUCH sharper and and became very happy with my purchase. Soon I took it for its first real test - I was photographing fishing boats in a harbour in very low light - I found that I was getting really good shutter speeds despite it being so dark - it really is a revelation when you use a fast lens for the first time.
There though I also discovered it's achilles heel - the autofocus performance in low light. It was really pretty disappointing, the poor little thing was hunting like mad and absolutely failing to focus a lot of the time, despite sounding like it was about to fall apart with the very noisy AF mechanism. I had to spend an inordinate amount of time finding constrasty areas of my scene to point it at to give it a chance to focus. Even when it finally achieved focus, around half of the shots were far from sharp, something I didn't discover until getting home. I even resorted to trying manual focus, something I rarely get good results with. It was tooth-gnashingly frustrating to have a beautiful scene in front of you yet not be able to photograph it because your AF is not up to it.
However, despite these issues I was still able to get plenty of decent photos as I took a fair few which made up for everything - it was very satisfying taking photos that good from a lens that cheap in very low light conditions.
To sum up as a novice user, used correctly you'll get great results - by that I mean learn about depth of field, learn to focus manually or how to "help" the autofocus in poor conditions and use it in it's sweet spot (f/5.6 or so). You'll be able to take pictures you'd never achieve with the kit lens and f/1.8 gives you excellent low-light performance and a tiny DOF if you fancy getting creative.