So how long by bus and is it worth 30 to get in? What cool stuff to see or buy?

In my opinion, no. That is based on last year's expo.

You're paying to go shopping. Once you get there there are hundreds of stalls, some from Europe, Africa and elsewhere, selling things. This isn't - as I thought it may be, like the Shangahi World Expo - It's a shopping arcade selling at extortionate prices. Another drawback, nothing to eat. If you are going, get something down you first, as the Expo Centre is in the middle of nowhere, nothing much to eat once there.

I'll give you some examples - Guantanamera cigar 100元 each, price on Wenlinjie 30元 price back home 100元 for a box.

I left with some 哈尔滨红肠, some dried squid and a headache.

I have to go tomorrow, If you like I'll give you a ticket. Save you from paying to get in and then regretting it. Let me know if you're up for it. To get there you can go by metro to ErJi Road, near the Burmese Embassy. Once there there are a few shared cabs that'll take you the rest of the way for 10元. Traffic will be awful.

In fairness it is the combination of two events. The 4th China South Asia Expo (why the new expo centre was needed) and the 24th China Kunming Import and Export Fair.
The Expo part pretty much wrapped up two days ago. That was not open to the public, but only to the Expo delegates.
The trade fair was opened to the public yesterday, and it is exactly that, a fair.
If you are willing to pay 30rmb entertainment value to see, and sometimes sample different kinds of food, you might even pick up a bargain. Last year, my wife came back with a set of solid wood, hand carved, traditional furniture from Thailand. A sofa/bench, 3 arm chairs, 3 tables. All at a very good price. Well worth the entrance fee.
This year she only came back laden with imported foodstuffs.

Great for shoppers, but as for me, I just hate the noise and crowds.

Concerning the Expo, I only know of one or two expats in Kunming who could contribute to it, or benefit from it. There really is little for Joe/Jane public at most international expos. The world expos are really in a different bracket, as they seem more about showboating for the host country/city; as such there is a lot to see and enjoy.

Went a few years ago. Noisy, crowded and prices are way out of line. I'll never waste time on this thing again.

Prices are negotiable and better deals are to be had on the last days of the trade fair. Think of it as a gigantic swap meet...

The traffics a nightmare around there right now!

The traffic seemed to be affected along Guangfu Lu, as far as Dianchi Lu and that intersection was bogged yesterday. In the morning, the only traffic direction that did not seem affected very much was the lake ring road, coming from Chenggong, and then heading out to west from the Expo centre. I should imagine all other routes in were affected.
A better location would have been Changshui airport area.
But last day today.

Thanks for all the replies and info everyone.