Samsung Galaxy S :: Phone Lagging / Takes Time To Access App - Returning To Home Page

I have now been using the samsung galaxy for a week now and there is only one factor that is letting down the phone for me and thats the lagging. I have no complaints about the camera even though its without the flash, the internet speed is top notch and the innovative swype makes life so much easier. However what irritates me is the time it takes to access an app or returning to the home page. It must take 30 seconds or more before the screen is loaded which is annoying when you want to do something in a hurry. This also occurs when someone is ringing me and I'm trying to answer, the phone freezes for 10 seconds. I,ve only downloaded around 10 apps so surely that cannot be the problem. I've got a week left before I have to come to a decision whether or not to keep the phone or return it back to vodafone and would like some advice or reassurance about this problem. Also out of interest I would like to know if anyone has encountered the same problem on the iphone 4. The one area in which the galaxy beats the iphone 4 is the price considering what you get with both however it may be worth it to use a phone that dosent lag.