Registrants are put in a "Catch-22" situation. They're expected to show rights or legitimate interests in the domain, which some panelists interpret to mean that they need to either already be doing business using the domain or have a detailed business plan of which the disputed domain is an integral part. However, who is going to put the effort and money into creating such a business plan surrounding a domain that is quite likely to be yanked away from you in the kangaroo-court STOP proceedings? A sensible businessperson is likely to wait until they have secure ownership of the generic-word .biz domain in question before they begin investing resources in it, but the panelists view such a situation as "lack of serious interest" and hold it against them.
In a particularly egregious decision, airport.biz was awarded to Apple Computer on the grounds of their having a trademark on "Airport" for a specialized technical product. The fact that the respondent said they were intending to use the name in the field of aviation, where it's definitively generic, didn't sway the panelist, who did a cut-and-paste with standard boilerplate arguments for lack of legitimate interest and bad faith on the grounds that there was no conceivable use of the name that wouldn't be intended to create confusion in the minds of Internet users between the respondent and the trademark owner. Maybe in the Looking Glass Universe, that's true, but where I am, when I head to the airport tomorrow to catch a flight, I'm not confused about misleading associations with an Apple Computer product. (Is Apple going to challenge any domain containing "airport" in the .aero TLD too?)
In another case, for bea.biz, NAF refused the respondent's request that the case be conducted in Korean, despite this being the language of the registration. The rules supposedly require the language of registration to be used unless both parties and the panelists consent to a different language, and the respondent here claimed not to speak English very well, but NAF brushed these concerns off and said that because the IP-claim confirmation process was conducted in English, this brought all registrants under the English language regardless of their registrars' agreement language, so the case would be conducted in English whether the respondent liked it or not. The respondent then failed to provide any response (maybe due to his lack of English skills, or because he saw it as a futile affair given that the process was stacked against him before the panelists even began to hear the case), and lost a default decision.
A few good decisions on generic-word cases were made, however, such as names.biz, kept by the registrant despite a claim of violation of a common law trademark in names.com. (Are they going to sue all .name registrants for being confusingly similar?)
On the whole, though, it seems like the resolution providers and panelists mostly regard STOP as a perfunctory process in which the mere existence of an IP claim provides strong rights on the part of the claimant that require a very strong defense to rebut them -- something few respondents are likely to be willing to put the resources into creating given how strongly the process is rigged against them.