Does anyone have any experience to promoting enterprise software on download site like tucows/softpedia? Is it worth to try?
I'm looking a site where I can promote my product (enterprise market/web developer market).
Software Directories like the ones you mentioned are very blunt instruments, you will find it expensive and very unrewarding.
As will all things the best way to market your product, is to engage with your target audience, be it Forums, Industry events (conferences etc) or simple targeted Ad-Words.
With that said, if you can get a presence on a Directory for FREE or relatively cheaply, it wont hurt you at all, in fact it can help you in ways that you may not have appreciated before, like SEO or general reputation.
best way in my opinion to market a product would be to Launch up a Google AdWords campaign on sites that fall into your niche... For eg. Freshbooks is an online invoicing SaaS for freelancers... a lot of freelancers use Joomla/Wordpress/Drupal etc. They have their ads up on Joomla website - which makes sense!
because, it is obvious that a lot of Freelancers would come on Joomla's official website... hence converting their ads into leads...
I'm not sure if you're looking for Free Promotion??
The directories work for some, but they will only work for some. Only so many items of software can be at the top.
For keyword targeting, look for long tail words where the competition is less and you can still go after the words that are at $10, just set a low max bid. Adwords, if your assumption on the right words is wrong, can cost you a lot and get you no where fast so measure the heck out of it.
I suggest looking at your competition's sites who are winning the SEO battles. Validate that its real competition, then if it is, see what other words they are looking at and what is linking in. Then analyze the link ins to see how to get mentioned on those sites so they can link to you. Get a feel for the type of inbound linking they have and generate ideas on how where to go to build your own linking campaign.
The right natural article, or the right customer blog can really make or break you with natural inbound traffic try to build some of these up while you assess where you can compete in Adwords.
The software directories work well for some, but can cheapen other software so assess that and do some experimentation. Often these sites will ask you to advertise but most software that advertises through there programs end up paying a lot more for there traffic then a good Adwords campaign and get a higher conversion with Adwords.