I've owned this phone now for well over 5 years and it works just as well today as it did the first day I got it. It was originally locked to Vodafone but I had mine unlocked and it now runs on O2.
There are lots of good points to the Sharp GX20 even though its quite an old phone now. It has a lovely large 240x320 pixel main screen which has a really bright, colourful display plus it also has a small 80x60 pixel external screen which is also very colourful.
It also has a camera which is extremly good for it's age, it comes as standard with a 640x480 camera which takes lovely clear photos, and can also record videos, however only upto 15 seconds. Not so good.
The phone has polyphonic ringtones, no MP3 i'm afraid as it's a little too old but polyphonic will do the job. It has space on the phone to upload some custom ones and even a composer to create your own. Custom ringtones can only be added by infra-red or USB however, as there is no bluetooth.
The battery is also very very good, it's a lithium battery and lasts upto 250 hours on stand-by, making it very reliable. Texts always go through first time as long as you have signal and there is lots of storage space.. Mine holds around 200-250 messages before it gets full.
The microphone is also very good, it's very clear and sharp and you can be heard even with noise around you. It also has a vibrate function.
Sharp GX-20s are now extremly extremly cheap. As they're so old you can pick these up now second hand for £10-£20 tops. I paid £60 when mine came out new so it hasn't dropped by much but it's still a good, affordable phone. It does however weigh 102g, which is a little bit more than most normal phones now, however the large screen easily makes up for it.
If you're looking for a phone that is easy to navigate, very customisable, has a good standard camera, sends & answers calls very easily and is good with sms texting then a Sharp GX-20 is a good choice. It's quite old and basic, but it'll get the job done without the fancy gimmics that cost a lot more.
What a load of rubbish, phone broke within several weeks of buying and then sharp had the nerve to try and charge me over £120 to fix THEIR faulty product. The overall performance of the phone is not great, main problems lie within things such as buttons as incredible unresponsive. Also microphone and speaker are unbelievably quiet. Please take my advice and do not buy sharp, there are a lot better phones and companies out there!!!!!