is 500mb data/month plenty for iphone 3gs?

I want an iphone 3gs, but i dont want to sign an 18 month contract. I also do not want a top up phone as they are a rip off. So I am trying to get an unlocked one from Belgium to use on 3 irl.

Failing that, my plan would be to buy one off 02 for 519 euro, and then sign up to their 30 day notice clear 350 plan for 50 euro/month.

This plan will give me 350 mins, 150 txts, and as my free extra, I would go for the free 500mb data/month.

So basically, I would be getting the same as the iphone350 plan, but only 500mb data instead of 1gb, and for 15 euro less/month, and no contract..granted I will have to pay a lot more for the phone.

Anyway...I use wifi at home/at work..any other time I would be using my 500 mb ...Id browse the net every day for about 45 mins, look at the odd youtube video..so is 500 mb plenty for that?

Thanks