Hello Mark,
Doha in September will be hot, very hot. Quite a lot of the ARAB local's will have left to other regions such as Europe because of the heat.
Having been to Qatar many times I can say its a lovely place to go to but plan on doing little as there is almost nothing but painfully white coral sand and dust. You must plan on a desert trip and I'd recommend going sailing as the water is bathroom temperature. If you go into the sun were about factor 5000 because you will cook.
As Neil says the Corniche is nice and there's a great hotel in the Sheraton Pyramid (I've stayed there perhaps 20 times). The Marriott has a reasonable Bar / Club but there's absolutely no shorts or jeans even if your a hotel resident. Whilst I like the hotel and it's great staff I wouldn't necessarily recommend staying there because its away from the town and basically at the end of the Doha Airport runway (I've stayed there perhaps 10 times). If you have some cash to spend the Ritz Carlton is beautiful but about 20mins away from Doha basically in the middle of nowhere (I've staryed there twice). There are some new Hilton and Intercontinental Hotels but I've never stayed at either.
The thing to remember is that this isn't Dubai and you are not in Kansas Toto. Qatar is less liberal and life is more restricted. Whilst it's not oppressive it is there. There are absolutely no bar's or pubs or club's outside 4-5 star hotels which you pay a significant premium for. Doha town itself is a massive building site of high rise buildings, the souq is much much smaller than that in Dubai or alternates such as Jeddah. I would say Doha is great to visit for a few days where you plan on doing relatively little but relaxing and experiencing a very differnet flavour of life.
One final tip I'd suggest is to see the cost differential of the executive rooms compared to the standard. Usually they aren't much more expensive but as you get free breakfast, daytime snacks and dinner nibbles plus in many free alcoholic beverages you can more than recover the additional costs....I certainly made heavy use of the Sheraton's, Marriotts and Ritz's executive lounges.
Cheers
Kym
