When I am some where with 3g my phone tells me. This appears not to happen much, on account I more more often than not in places in the middle of nowhere, rather than slap bang somewhere.
and when I am somewhere I am usually able to access free wifi - which is faster than anything with a G in it.
So if I get a phone soon through O2 or similar, it won't be 4g compatible? Does that matter? Do I wait till its become standard or simply ignore it as an interesting bonus for vair important city types 
Please use small words so I have a basic understanding before the sales people attempt to bamboozle me.