Sounds like a non-qualified deferred compensation plan. I participate in mine, so I'll relay what I know.
Negatives
1. These accounts look like other retirement accounts, in that you see contributions and matches, and you pick from a short list of investment options. However, they are not, although you'll want to read the plan documents for your wife's to be sure. My documents indicate that the company is under no obligation to actually invest the money they way I choose. While someone else may be able to chime in with some specifics, I believe that basically the deferred compensation essentially stays as company property, and that the accounts in your name are sort of a fiction, which are used to keep track of what they owe you. But you don't actually own the account, and in all likelihood there is not some separate pile of money/investments just for you. Instead, the program is funded by the company, the account managers are paid, and the company keeps a tally of what's supposed to be in there, and balances that with what it needs to pay out based on people leaving/retiring.
2. Based on the first point, these accounts are risky. If your company goes bankrupt or possibly even undergoes some major change like buyouts, it's possible to lose some or all of the account value. Definitely do not put money in here that you may need in the short to medium term, and in reality, you should probably at least accept the small possibility that you will never see again.
3. The investment options are often substandard with higher ERs than you would probably like.
Positives
1. There is really only one, and that is to defer paying taxes on the contributions, matches, and capital gains in these accounts until some later point. The caveat is that you will have to take the account as earned income at some point. If you can do it in a year when you have little to no other earned income, great, but this requires that a) you probably need to be in a high marginal tax bracket when you make the contributions and b) you have at least some reasonable level of confidence that you can control your exit from the company.
2. If you get matching, which your wife's plan does appear to do (mine has a different matching structure than your wife's), then that's potential additional income, not unlike the argument used regarding 401k, except that again, it's not really your money until you leave the company, retire, or otherwise trigger payment of the deferred compensation.