That's not a real shocker, considering the current economic climate. But it's not because of trouble at EPiServer: in fact, the vendor seems to be doing well, and apparently, all available shares were placed. The main reason to withdraw seems to have been a volatile stock market. In other words, if one of the reasons to go public with your company is prestige, it doesn't look so good if immediately afterwards the share prices tank. Even if it's because the stockbrokers in Stockholm are in a general panic about the market as a whole, and not your shares specifically.
So should this worry you if you're a current customer or looking for a CMS? Not at all. If anything, I would argue it's in technology buyer's interest for EPiServer to maintain its steady growth, rather than the company jumping into the shark-infested waters of mergers & acquisitions. You could sympathize with EPiServer's disappointment, but other than that, this means business as usual.