eCommerce - Netsuite is abysmal at websites, and shopping carts. Opensource programs such as Magento, and OScommerce from 2005 are more updated and useful than anything netsuite has to offer in the ecommerce module. It is extremely buggy and slow! You no access to page layout and content other than some basic forms, or if you pay extra for the ability to create custom suitescript pages. Stay away!
Integration - Netsuite has the worst API integration I have ever seen from a major web software system. The documentation is horrid it takes months of research to build anything useful. It is also the slowest API I have ever seen you share your servers with other Netsuite Customers, thus all of your requests have to go into a Queue to be processed. Every other web API I have ever used as been nearly instant. Netsuite locks you down to limited accounts that you either have to pay extra or share with a user for API access, and you cannot run multiple requests at the same time! If you do not que a program that has multiple employees making requests they will all collide and fail.
You have to pay for Database access, we were never able to test this for usefulness as we were promised the ODBC module for all of our issues and it never happened. That being said without ODBC module you have NO database access what so ever. Due to Netsuite being a web program you have limited to no access to your own content! From an Senior IT perspective I highly recommend a software that you have full access to all of your data!
The reporting system, though robust, is extremely confusing! It takes hours to build simple reports! I am able to open up a raw SQL database and build reports faster than I can on a supposedly "user friendly" report building GUI. Also if you want to do pivot and cross reporting you will have to pay to upgrade to a better reporting module....
Terrible Integration! Due to Netsuite being a Browser based program its ability to integrate with any program or devices outside of netsuite is horribly limited and always requires custom SuiteTalk programing code, or a 3rd party vendor program that "hack integrates" by screen scraping or simulation a browser to function. A great example of this is OzLink which does it best to provide Shipping integration with FedEx Manager and Scanning guns, but is extremely buggy due to Netsuite's poor ability to integrate with anything well.
*****An unexpected error has occurred***** - this is the most common error you will see in netsuite... For everything and anything.
Support is terrible we had the very expensive gold support for 3+ years. They are great and answering simple questions that any seasoned Netsuite Administrator could solve. But when something is broken say Google Checkout, your problem gets filed as a future upgrade and then either ignored or told years later that they are dropping that feature. In all of the years with Netsuite they have never fixed any broken feature for us.
Data Transfer. Getting data into netsuite is easy, for a price... Get data out of netsuite is near impossible, I Highly recommend you keep external backups of all your data incase you ever need it for any other systems.
Transactions cannot be locked or assigned to employees. Users can easily open the same orders other are working on.
Kits are horrible!!! If you do anything with kits you are at a major risk with netsuite as they over complicate everything. If you change a kit that is being processed it will break every transaction attached to it until it is updated. There is a mass update for this but it doesn't work consistently.
No per item shipping. Simply put if you want to discounts on a single item for shipping or give free shipping on certain items for only certain shipping methods its not possible.
Promotional Codes (Coupons) and Discounts are convoluted and require you to set them up in two separate locations if you want decent reporting. Also the promotional codes are not flexible when trying to target certain products or groups of products, or provide individually free shipping.
The system is very slow. Even on a commercial fiber connection Netsuite runs very slow, where as our previous stand alone system was nearly instant with processing orders. You will often be waiting for browser loading on anything and everything, especially during peak operating hours.
All external devices are difficult if not impossible to integrate such as POS and Product Scanners.
Their email system is prone to being blocked as spam.
You will run out of storage space and have to upgrade if you do a lot processing and customer volume.
Trying to get simple reports such as "how many Sales Order were shipping by who" has even taken me a Senior Developer days to figure out, even to the point where I would rather use my own Netsuite API that I build to pull the data out and build the report myself.
In order to get Netsuite to function the way you would like it will take years of customization, and sometime I wonder if the same efforts applied to something like free SugarCRM would have the same results but for a near fraction of the cost.