I am sorry to say this, especially after using VM extensively for many, many years and having donated a few times for projects during VM1.1 days. I will be stopping developing any sites using VM2 for the forseeable future and on the next opportunity for each client will look to migrate to a new ecommerce software once chosen.
This decision has not been taken lightly either, having jumped on the first releases of VM2 eagerly, and assisted in the bugfixing forum finding some of the numerous early problems I expected a lot of usability issues to have been dealt with by now and for my general experience to have improved enough to feel confident to donate yet again for each client site I create using the software - this has not been the case.
The whole custom fields system is still a joke, a dealbreaker for almost all users apart from those that have learned the 'trick' to using it. NO ecommerce system should be this badly thought out that a year after it launches the majority of complaints are for one, quite frankly, huge area of usability that users in general cannot work out. The terminology used is overcomplicated, the options are overcomplicated and too rigid, the actual functionality is poor at best - it does not work as it should.
The shame here is that most of the really annoying, but only annoying, bugs have now been ironed out. There are lingering ones like the lack of ordering on certain sections - payment systems don't seem to obey the ordering you set and of course it goes without saying that the custom fields section behaves like IT wants to. 90% of the typical functionality of top level ecommerce systems is there - nailed, the problem is the final 10%, where people want to offer more complex options than 1 product SKU, 1 option, 1 price.
I have two client sites, migrated from VM1.1 which was working great but done because Joomla 1.5 was coming up to EOL and they were due a bit of modernisation. One had a very simple multiple dropdown with options either plus or minus priced from the parent, others had to have a dropdown where the prices changed so often that plus and minus would not work so the equals function worked flawlessly to keep a track on prices - why on earth was this removed - totally and with no viable replacement? I can no longer have a parent product priced at zero and products individually priced - why not? That is a fundamental function.
A second site I have needs much more complex configuration, ideally instead of dropdowns of manually created items I would use sku codes to pick up already existing products in the shop, instead I am trying to use PRO's plugin to create dropdowns because a third party plugin that actually, as good as it is, still does not allow price input within the plugin config, is the best option available. It is almost as if the custom fields was disregarded for being too difficult and hashed together without thinking through how it is used. I cannot figure out how I am supposed to offer a customer the option of paint finish or powder coat finish with two completely different colour ranges - if powder coat is chosen, paint is disallowed and vice-versa. That should be a simple function.
The final nail in the coffin for me though im afraid is just how few threads get resolved with a genuine developer response rather than the mutterings of a handful of frustrated, amateur coders who are just trying to make their sites work. If documentation and usability are not working to help questions to problems the user will always jump on a forum as a port of call but it seems that the forum is less answered here than ever before, I am not really a poster for problems, but I read pages and pages of single 'please help me I cant do....' threads that go unanswered by people that would know (hopefully) and unfortunately the custom fields and product creation side of it suffers particularly badly for being ignored or avoided.
To those of you who use VM and have never donated anything but still feel like complaining, that is one of the issues with a large open source project like this. Developers on these projects can only afford to spend time if they can balance bills and home life which usually means having to work, every time you start a project or get a little help how about sending a little funding back to help them move the project along? I must confess to not donating anything since the launch of VM2 - purely because it has actually cost me more money and time to try and configure than I have made for a few clients, I did want to give something back to the project but for now I am left looking for a cost effective way to migrate clients and spend my own time learning an new ecommerce software, VM2 has not got easier to use in a year and I feel it is going to stay this way.