iphone lagging

My recollection is that the 3G, even with the 3.0 system, slowed significantly when jailbroken. I've also read in quite a few places that the 4.0 system is rather slow on the 3G. Put the two together and "lagging very bad" sounds about right. If it were my 3G I'd be looking into the possibility of rolling back a couple of versions, like to 3.1.3 or so. At least 4.0 wouldn't be slowing it down to start with. But even so, if you jailbreak a 3G, it's going to slow it down and it will continue to slow over time. If you have to unlock it, which requires a jailbreak, you may want to consider getting rid of it and getting a 3GS which is less affected by jailbreak.

 

3g with ios 4.0 = sluggish + jailbroken = maybe even slower

 

It’s a tradeoff. You get more sluggish, but you can do more. If you reduce some of the things you can do, it’ll speed up.