Your consultancy won't go public, absent another dot-com boom. Recent history is littered with consultancies (Scient, Viant, Sapient, MarchFirst, Lante, iXL, Razorfish, Proxicom, Organic, etc.) who all went public then tanked (or at least, seriously underperformed the market) when the bubble burst.

Why not? General IT consultancies are a poor investment - they tend to have little in the way of proprietary IP or hard assets, so they're only worth as much as their employee/client base. Even that's fickle - if new management/owners make changes that alienate either of those constituencies, that value can evaporate overnight.

There's the possibility you could get bought, but you'd have to be in a high-value product/client space for this to make much sense. It also depends on the attitudes of majority owners, who are probably far too accustomed to running an independent business to want to sell out to someone else, even in response to offers you might consider very good.

Should you get bought, it's likely the new owners will make senior management (including you?) sign agreements to stay on and/or not flip their shares for a set period. You already sound like you're itching to leave - are you sure you'd want to stay on longer than five years?

You won't be in much position to see any return on your shares absent a sale or public offering - foregoing warnings about dilution, Hollywood accounting, different share classes etc. all apply. (Possible out: google "Rule 144" regarding sale of closely held stock after two years. Good luck finding a buyer though.)

My opinion: walk; your sanity is worth far more than the meager chance of a payout.

Disclaimer: used to work for an IT consultancy; spent good money for shares of closely-held stock, on which I'm now unlikely to see any return. Now an independent contractor; too happy to be bitter.