Theres lots of talk of buying "targeted" traffic for your website, but lots of these sound pretty bogus to me... I mean most of them are just from sites like Bux.TO etc which all you have to do is see a site for 30 seconds, I want people who are actually interested in my site coming so they register and stay, not just for 30 seconds.

Any advice?

don't waste the money, just spend time promoting your site yourself.. you will bring more users that way.

Yeah, I think all sites just require the people to view the website for a certain amount of seconds, and I don't even view the site when I do that, I just leave it open in another tab and let the timer run out. Promote your site in other ways, that are cheaper. Such as linking in your sig, buying ad space, Google AdWords, etc.

Some traffic exchanges really worked in the past but these times have gone, now there are no quality exchanges I'm aware of and most of them have people who only visit them to make credits and exchange them for money or drive them to site with CPM banners for example.
Some time ago I've got promotion from my friend who gave me nice amount of credits on one traffic exchange, and I've specially did a test tracking what these people actually do on my site, and I have to say that all of them visit single page and not even do single click on the link which should say that such traffic is absolutely useless.

Dough Boy is right, participating(not spamming) on forums, exchanging links with sites relevant to yours, buying banners on relevant sites, AdWords or similar companies should do the trick and save on your costs too.

It isn't worth at all, although once or twice it did work for me, but otherwise, it is not worth the money you pay...

Its just wasting money. And same for me, I let the timer run out when I open the 30 seconds websites on AdBux and things like that.

If you want quality traffic to your site, invest on Google Adwords, Yahoo advertising - these are trusted names in getting quality traffic to your site. If you just want hits to your site join free link exchanges, traffic exchanges, banner exchanges. Don't waste your money in buying traffic from timed view sites - its not worth it.

Is it true that Adsense can detect and ban your account if you use autosurf and other traffic exchange programs on your web?

^^ Yes it is very true!! Happens to quite a lot of people actually

If you want targeted traffic then buying it from PTC ( Pay To Click) sites may not work. If you want to advertise other similar sites then it's probably OK. But for affiliate marketing/selling your product , it may not work. It is better to use Adwords and use SEO to bring search engine traffic.

PPC traffic can be very useful but the sites that just send random traffic to your site...? no thx