We have just had a great 3 hour tour of the main city attractions. Boy what it worth it!
There is no way we could have had just great insight to the city on our own. We now feel set up to explore the whole area on our own - well armed for the market traders!
Beware though! It seems that all the guides take you 'favourite' stores for your own personal tutorial about spices, carpets, trinkets and such. They are all just an excuse to sell you there wares. Non threatening but the carpet store manager was a formidable salesman that would well in any secondhand car dealership!
Oh, and our guide warned us not to allow any of the sideshow snake charmers to place a snake around your neck for a picture - unless of course you don't mind negotiating the fee of the picture before he takes it off you!
Anyway, do the guided tour!