Hutson was quicker with typing a reply, but here is my opionion, too:

its too slow! Joomla themselves recommend new sites be built in J3 and I have rolled out many. I need a cart now and I don't want to have to use J2.5 and face both a VM / Joomla upgrade so soon after launch.
I disagree. Joomla 3.x still is in its infancy stage (like 1.6 and 1.7 was for 2.5.x) and many things are subject to change until the long term support version 3.5 will be released. Versions prior to 3.5 are supported only for a period of 7 months each and are primarily meant for developers who want to test their extensions and users who get along with Joomla 3.x built in features. A comprehensive shopping cart extension like VM2 contains many thousand lines of code which have to work reliable for professional shops. It also has to maintain compatibility with important third party extensions like i.e. payment solutions. It's not just a tiny extension with a hundred lines of code which can be adapted to a new Joomla version within a few hours. And at present it is not even clear, which versions of external libraries (i.e. Mootools, JQuery, Bootstrap, etc.) will be built into Joomla 3.5. So from the developer's point of view, it doesn't make a lot of sense to waste a lot of time to reach compatibility with a Joomla version for which support is ending soon.
Once you have your own live shop with maybe a 1000+ products, I bet you will experience that following all available updates quickly becomes a pain because of the amount of work involved and the number of avoidable compatibility problems it generates. BTW - Joomla's own website still is running on version 2.5 for similar reasons.
VM is slipping down the rankings on the Joomla Extensions site too .... Its a cop out to say you are going to wait for a stable 3.5 release .... too late then. You are behind the ball .....
For experienced VirtueMart users it is pretty obvious that the ranking in the JED is primarily due to a lack of knowledge on the part of it's novice users or semi-professionals who are upset because they were unable to implement a (not yet existing) very special feature their client insisted on. VirtueMart's strength is it's flexibility. It primarily aims to serve as a 'shop construction kit', which comprises a longer learning curve than some of it's competitors aiming at shop owners who just want a simple, easy to use standard shopping cart solution, that works out of the box.
This is imho the major reason why certain other shopping carts are ranking higher in the JED. The users of the VM's competitors made the right decision concerning what they need, while most negative reviews for VirtueMart are coming from users who made the wrong decision for their individual needs right at the start.
The vast majority of many thousands of happy VirtueMart users never get the idea to write a review in the JED. Last time I searched for the number of VirtueMart 2 shops in the internet using one of Google's advanced (hidden) search features, it came up with 189000 english language VM2 shops.