But free advice from a non-lawyer is worth what you pay for it, so consult legal counsel for more definitive info. I just don't see the point of mentioning your competition in the meta tags. I had one of our competitors do this, once contacted they had to remove it. Thay had our TM, full website name including product names. But like littleman said, if it is done appropriatly right on the page, there is nothing unethical about it.
Competitors mention each other all the time.
Agree with Brett, nothing wrong with making product comparisons and providing people with good information. That happens all the time. If the competition has a well known generic name tha tyou can weave in without it being overly obvious, might be allright. Your company is named SuperX and you sell widgets. I can't begin to count the number of times I've gotten a small company rankings for a competitor's product names.