I have a 3GS Iphone that I was/am perfectly happy with, the problem is that its OS has been continuously upgraded and now runs 6.1 and its really slow/jerky/clunky to the point were its unusable.

A last resort is to try a factory restore on it. The phone is sync’ed to a pc and via Icloud.

If I do a full restore will it be lacking anything afterwards? email/messages etc? or does it back up everything?

TIA

I did a full restore on my 4S iPhone about 6mths ago. I had got bored of the pointless (IMO) jailbreak so wanted it back to normal. I’ve not noticed anything missing. It did take ages though. At least 2 hours, if not longer.

Make sure you have a full backup, in iTunes not on iCloud. Make it a password protected backup as then it can also backup your account passwords etc.

If you restore from this backup it should contain pretty much everything. I’ve done it a couple of times and never noticed anything missing.

Thanks for the info – will try it tomoz and see what happens!

The only thing it won’t back up is your music. Photos and everything else will be ok, but it doesn’t hurt to save them into iPhoto just to make sure, if you don’t already do that automatically.

I stand to be corrected but when I upgraded from iPhone 4 to 5 I did a factory reset on the 4 so that none of my personal information was on there when I sold it. The phone didn’t factory reset to the iOS it was on at brand new but stayed on the latest iOS installed on the phone. For example, when I got the phone the iOS didn’t have that passbook app but after factory reset it still had it, it just thought it was a new phone.

That’s true, I think, but the point of doing a factory reset means that any cruft that’s accumulated over a series of updates, both OS and app, will be completely cleaned out, so it should run quicker and smoother.
Doing the same thing to desktop machines is often advised, because data gets fragmented and spread across HDD segments. Not sure how that squares with SDD’s and flash memory on phones and pads, but it certainly can’t do any harm, either.
Do a backup, factory reset, then restore from last backup. Easy as, really and can often help. It’ll be interesting to see how my old iP4 reacts to having iOS 7 installed, but it doesn’t have much stuff on it anyway, just an iPod and satnav device, and backup on a different network.